Petrol Consumption....AGAIN - Adam {P}
Morning all,

I've talked about this countless times but after having to put £50 of juice in every week I've decided to conduct an experiment.

For the next week, I am not going to exceed a single speed limit - that includes the motorway. It's going to be long, hard and tedious but in the interests of science, I'm going to do it.

The tank is pretty much empty at the minute so it's a good time to start. I've tried driving slower before but not really noticed much difference but 200 quid a month minimum for Uni and back and the odd journey seems a little excessive; especially when you take into account that I don't have a life!

I hope, in a way that I don't notice a change but we'll see. I'll be sitting in 3rd a lot more as it bogs down on most roads around here in 3rd but the motorway will probably make up for it.

And so it begins.


--
Adam
Petrol Consumption....AGAIN - Garethj
Good experiment! I once kept a note of how much fuel my Jaguar XJ-S V12 was using over a month, rather than just blindly filling it up every time it was needed.

Once I found out I sold it :-(
Petrol Consumption....AGAIN - L'escargot
I don't think that it's only high speeds that are your problem. I think that it's also large throttle openings and low gears. Try moderating your acceleration and changing up as soon as possible!
--
L\'escargot by name, but not by nature.
Petrol Consumption....AGAIN - cheddar
>>
Try moderating your acceleration and changing up as soon as
possible!


Light throttle openings and a few revs are better than letting it labour in a high gear.
Petrol Consumption....AGAIN - RichardW
£50 at 85p/litre is nearly 59 litres - my Xantia (TD @ 40 mpg)will do about 530 miles on that, or 27,500 miles a year! Either you drive a long way or your Focus has a bit of drinking habit. How many miles a week are you doing Adam? Time to go diesel???? :-))


--
RichardW

Is it illogical? It must be Citroen....
Petrol Consumption....AGAIN - L'escargot
£50 at 85p/litre is nearly 59 litres - my Xantia (TD
@ 40 mpg)will do about 530 miles on that.....


So will my 2 litre petrol Focus ~ I think Adski's is only a 1.8 so he and I must be doing SOMETHING different!
--
L\'escargot by name, but not by nature.
Petrol Consumption....AGAIN - L'escargot
Light throttle openings and a few revs are better than letting
it labour in a high gear.


I wasn't suggesting letting the engine labour, merely changing up as soon as is reasonable and practicable.
--
L\'escargot by name, but not by nature.
Petrol Consumption....AGAIN - Garethj
I wasn't suggesting letting the engine labour>>


That's what works for minicab drivers. 1000 rpm in 4th and accelerating out of a roundabout? Quick! Change up!
Petrol Consumption....AGAIN - drbe
That's what works for minicab drivers. 1000 rpm in 4th
and accelerating out of a roundabout? Quick! Change up!

>
Oi! Watch it! ;-)
Petrol Consumption....AGAIN - chris_w
Used to get 26 mpg on overage from my Focus 1.8 zetec.... think a Cheiftan Tank returns better economy than mine.
Petrol Consumption....AGAIN - VTiredeyes
do it ad. let us know the results.
my megane sport tourer is returning 44mpg on computer, but i get 600 miles from a tank.
60L is 13.3 gallons
so at 50mpg i would get 650, so i must be getting about 45 mpg.
Petrol Consumption....AGAIN - Round The Bend
Heavy breaking will affect MPG as will wrongly inflated tyres. Wow! With all these tips you should be getting 70 mpg!

Petrol Consumption....AGAIN - WhiteTruckMan
Its very simple.
1-get into top gear (not the tv program)as soon as practically possible.

2-stay in top gear as long as possible. award yourself a smack in the face every time you have to change down.

3-drive like your favourite dangly bits were between the gas/brake pedal and your feet. the harder you use them, the more your eyes are gonna water.

4-drive everywhere as slowly as possible while keeping in top gear. For maximum annoyance factor to others, wear a hat and smoke a pipe.

5-it sounds corny, but read the road ahead. not just 10 feet past your bonnet, like so many seem to do. if theres standing traffic up ahead, dont drive up to it. take your foot off and coast up to it. so what if some ignorant git passes you? it only puts you back a couple of car lengths, and doesnt really increase your journey time all that much.

WTM
Petrol Consumption....AGAIN - Bill Payer
4-drive everywhere as slowly as possible while keeping in top gear.

I know the above is somewhat TIC - but isn't there an 'optimum' speed to drive at in top gear - something like 55MPH? - so that all the engines losses don't have a significant effect?
Petrol Consumption....AGAIN - VTiredeyes
56 mph

Petrol Consumption....AGAIN - Altea Ego
It varies from car to car, but yep 56mph in top gear is considered the average most economical speed.
Petrol Consumption....AGAIN - pdc {P}
I posted here last summer that I was doing such an experiment, and updated on a regular basis. I am still driving around at or below the posted limits, and not accelerating hard from junctions/lights etc. I'm saving about £50 per month, which is a couple of cheap holidays abroad in the sun over the course of the year.

I'm also less stressed for it, especially on the motorway.
Petrol Consumption....AGAIN - VTiredeyes
yes PDC, i have found that.
in the last 16 months, since having to pay and claim fuel, i dont drive everywhere at 100mph.
i drive at 60-70 on mways, and drive as best i can, looking forward more, to see when to use brakes less and not accelerate hard.
and i am soooo less stressed.
and no points on my licence either.
:-)
Petrol Consumption....AGAIN - chris_w
On my new car the MPG displayed on the screen is directly correlated to how hard I push the accelerator - I seem to be able to drive at 60 or 80 and still acheive the same MPG.

Always thought that the 56mph thing was a bit of a red herring - is that not the speed they suggest purely for working out the mpg? surely on a 3.0L+ engine it would be completely different?

Petrol Consumption....AGAIN - Big Bad Dave
No it?s mostly to do with overcoming wind resistance and rolling resistance throughout the drive train. That?s where all your money?s going. Air is the real killer, you get diminishing returns the faster you go. So 180bhp might get you to 150mph but to get to 200mph you need more like 500bhp.
Petrol Consumption....AGAIN - BazzaBear {P}
As I understood it, the most economical speed to do would be whatever speed correlates to maximum torque in top gear.
Unfortunately, in my car that would be exceeding the speed limit...
Petrol Consumption....AGAIN - Garethj
No, it would be the lowest revs your engine is able to keep going at without labouring so you have to change down. I've got an old Autocar test of my car and it will do 35mpg at 60mph, but 70mpg at 30mph!! Although anything more than a 1:100 slope would soon knock that on the head.

56mph is 90kph which is one of the DIN standards for measurement.
Petrol Consumption....AGAIN - Altea Ego
And chosen (dont forget DIN is a standards body owned by the people that use it - car companies in this case) becuase it gives the best average figures.
Petrol Consumption....AGAIN - Big Bad Dave
If you?re curious about how hard your engine has to work at high speed, stick your hand right out of the window at 100mph. The force that has just torn all the ligaments out of your shoulder is the wind on just a few square cm of your hand. Your car will be presenting maybe 6 square metres to the wind. And imagine what it?s like for trucks and coaches.
Petrol Consumption....AGAIN - chris_w
Don't see that many trucks doing a ton :-P
Petrol Consumption....AGAIN - v8man
If you?re curious about how hard your engine has to work
at high speed, stick your hand right out of the window
at 100mph. The force that has just torn all the ligaments
out of your shoulder is the wind on just a few
square cm of your hand. Your car will be presenting maybe
6 square metres to the wind. And imagine what it?s like
for trucks and coaches.

Try riding an naked motorbike at 100mph. I used to have aneck like Tyson!
--
\"Nothing less than 8 cylinders will do\"
Petrol Consumption....AGAIN - Number_Cruncher
In order to rigourously understand how to get the best efficiency from an engine, you need to arm yourself with some dynamometer test results, and plot out a number of graphs. (It is highly unlikely you will be able to get enough data to do this outside a manufacturer's engine lab!)

If on the x axis of the graph, you mark engine speed in rpm

and on the y axis, mark up in BMEP (Brake Mean Effective Pressure - consider it as a measure of load)

On the graph plot contours of constant BSFC (Brake Specific Fuel Consumption - how much power you get per unit mass of fuel burnt)

The graph looks a bit like the skins of a sectioned onion. You get the best power per unit mass of fuel burn in the centre of the "onion".

For petrol engines, the centre of the onion is typically close to the maximum torque speed, and about mid load. This area of optimum economy is quite small for a petrol engine.

For a diesel, the "onion" is more oval, stetched out in the direction of the speed axis - they tend to be less sensitive to manifold tuning effects as they typically run so weak. The centre of the onion is also closer to full load than in the case of the petrol engine.

So labouring along in too high a gear may not be making the best use of your fuel - equally, screaming along the back roads near the red line may also not be conducive to good economy.

In the absence of all of the required data, and the time to plot it all out, biassing your driving around the maximum torque speed of the engine is not a bad place to begin IMO.

number_cruncher
Petrol Consumption....AGAIN - cheddar
Looking back up the thread and the talk of 26 to 30 mpg me thinks diesel is making more and more sense, approx speaking fuel is getting on for £4-50/gallon at which price 45mpg = 10p/mile and 30mpg = 15p/mile, over say 1500 miles a month the difference in favour of diesel is £75-00!
Petrol Consumption....AGAIN - Adam {P}
Wow. A lot of replies. Some scientific, some funny, some both!

I did think there was a problem but when you sit down and add it up, I suppose I am doing quite a few trips. Still not enough to justify the consumption I'm getting though!

Mum to work every morning and back each evening = 15 miles

Me to Uni every morning and back every..ahem...lunchtime plus one day off from there = at a guess, 30 miles. (I have set the odometer to zero so I can verify later.

So essential trips add up to roughly 195 miles a week. Miscellaneous trips - mafia deals, mate's houses etc... probably add another 50 on that to be safe. So 245 miles a week is equating to (very, VERY roughly) £50 a week. Now when I say it like that it doesn't sound too bad. Especially when I will confess, I like the sound of high revs!

But that's 980 miles a month. Now I know I do about 17k a year so I've cocked up somewhere in my calculations. I'll be far more accurate once I get some real figures. I may do this for a month just to be doubly accurate although it did kill me going that slow on the motorway before. Flatbeds were overtaking me!

I just can't bring myself to get a diesel. I know they're far more advanced but all your TDis and TDCi's and CDTI's just sound....un-petrollike to me! When I get a bit more sensible, I'll probably get a diesel but I have to go through a ridiculously expensive and fast car phase first! ;-)

Many thanks for all of your replies. I'll get back to you with some hard figures later on in the week.

Thanks,
--
Adam
Petrol Consumption....AGAIN - Marc4Six
I once checked my fuel consumption over a period of 4 months.

Results:
Miles driven 3517.5
Gallons used 149.17
Average MPG 23.58
Best MPG 27.64
Worst MPG 20.67

Conclusion:
Don't check fuel consumption again. :-(
Petrol Consumption....AGAIN - thallium81
Hells bells Adski, you seem to be getting less than 20MPG, my 3.0L suby does better than that. Are you sure everything is working properly?
Petrol Consumption....AGAIN - David Horn
How come petrols use more fuel on wide throttle openings when the pedal doesn't directly influence the amount of fuel getting into the engine?
Petrol Consumption....AGAIN - mfarrow
the pedal doesn't directly influence the amount of fuel getting into
the engine.


But surely it does? Wider throttle opening means more air/fuel mass can flow past it into the engine.

--------------
Mike Farrow
Petrol Consumption....AGAIN - jdc
Adksi

Diesel doesn't have to be boring y'now !

I picked up a new Fabia VrS yesterday (to complement with our Subaru Outback 2.5).

The Fabia goes like stink ! Today, just for fun, I drove completely round the M60 from home. Exactly 50 miles - averaged 57 mpg ! Mid-gear acceleration is phenonemal, completely intoxicating and mad, mad fun .....

The expression on a guy behind was priceless - pottering along in 40 because of road works near Sale - then BAM ! Roadworks finished, foot down and 70 was there in a nano-second ....

Wonderful, wonderful little car

jdc
Petrol Consumption....AGAIN - P3t3r
I may do this for a month just to be
doubly accurate although it did kill me going that slow on
the motorway before. Flatbeds were overtaking me!


Imagine what it's like for us law abiding citizens, I drive like this all the time :(
Petrol Consumption....AGAIN - rtj70
Had a trip from Stockport to South Wales at the weekend in my Mondeo TDCi (which is now due it's 25k service too, so oil needs replacing but it's not 18 months old yet).

The trip down, went the scenic way through Wales with first bit on M56/M53. Brim to brim I got about 47 mpg (actual) for the 200 miles. So about £17 (89.9p/litre) and I'm not light on the throttle but didn't speed.

The way back, motorways so longer but got (brim to brim) 49mpg and about £17 (87.9p/litre) again. And the climate control was on too.

Admittedly mostly free flowing traffic but that was about 430 miles for £35. And there was also some hard acceleration at times too.

I used to get better than Adski in all of the following: Golf GTi Turbo, Audi A4 Sport 1.8T and two VW Passat 1.8T Sports. Get it checked out... actually the second Passat was only okay until the air-con failed and got the unit replaced and then it was so much better.
Petrol Consumption....AGAIN - tyro
In the absence of all of the required data, and the
time to plot it all out, biassing your driving around the
maximum torque speed of the engine is not a bad place
to begin IMO.


Sorry for asking a stupid question, but how do I know what the max torque speed of my car's engine is?
Petrol Consumption....AGAIN - Number_Cruncher
It's probably listed in the specifications section in your car's handbook, perhaps in the form XX Nm @ YYYY rpm.

number_cruncher
Petrol Consumption....AGAIN - tyro
It's probably listed in the specifications section in your car's handbook,
perhaps in the form XX Nm @ YYYY rpm.


number_cruncher


Can't find anything there. The Berlingo Handbook, however, is about the worst I've ever seen.

What Car? gives a figure of 108 lb/ft at 4000 rpm for pulling power. However, I can't believe that driving at 4000 rpm would be the way to maximise fuel economy - I'd be way over 70 mph in 5th gear.
Petrol Consumption....AGAIN - edisdead {P}
Number_Cruncher's dynamometer graphs are purely a way to measure an engine's power output and efficiency for a given load and RPM range, without taking into account the effect of the resistive drag force determined by the speed the car would be travelling if it was on a real road and not a test rig.

Running your engine at peak torque rpm does maximise your efficiency on the rolling road, but efficiency here is a different kettle of fish to MPG, which is what we motorists are interested in. Travelling in top gear at a constant speed on the motorway, you will achieve optimum MPG at an engine speed well below max torque RPM due to the additional aerodynamic drag force.

The golden speed (often around 55mph) is determined by the relationship between the different components of the resistive forces which are proportional to your speed and the square of your speed.

More detail at www.howstuffworks.com/question477.htm

Ed.
Petrol Consumption....AGAIN - Number_Cruncher
Number_Cruncher's dynamometer graphs are purely a way to measure an engine's
power output and efficiency for a given load and RPM range,
without taking into account the effect of the resistive drag force
determined by the speed the car would be travelling if it
was on a real road and not a test rig.



Indeed, I agree there is more than engine efficiency in the equation to determine miles per gallon - among many factors, aerodynamic drag and this country's speed limits have their influence.

The aim of my post was to suggest that low revs and low load are not always the ways to get the best performance and efficiency from an engine.

From observation, and from the results of a (now quite old) experiment, people tend not to use engines in their optimum speed range, tending to change up too early. I don't know if there is some acoustic, or NVH reason for this, or if it just a hangover of the idea that slow engine speed is good and efficient. Any ideas?

number_cruncher
Petrol Consumption....AGAIN - P3t3r
I don't know what car you've got, but it sounds like a lot of fuel. Driving slow will not necessarily mean you will get much better fuel consumption. In my opinion by slowing up you'll reduce the amount of 'wasted accleration'. If you drive slower you are likely to need to brake less. Whereas if you drive fast you'll brake more often, and then need to accelerate again to get the speed back.

In my opinion I don't think it's a good idea to always use the highest gear possible. Lower gears are always more responsive, and keep the engine happier. I used to drive around in 4th at 30mph, and got a good few more mpg, but it was a lot less responsive, and the engine wasn't so happy. In 3rd at 30mph the car can quite happily take small slopes, and if I slow up a bit I don't need to change gear.

Driving slower, and anticipating hazards is always a very good idea. If a light is red slow up before, and if you're lucky it'll be green before you come to a stop, this means that there is less acclerating to be done. In fact slowing up for red lights will quite often get you past the lights quicker, it certainly doesn't slow you up.
Petrol Consumption....AGAIN - Big Bad Dave
When I have my mother in law in the car I get 2mpg less.

Perhaps Adski is a little er... overweight?
Petrol Consumption....AGAIN - DavidHM
Adam - at 17k a year and 85p a litre, you're getting a back of the envelope (okay Windows calculator) 28 mpg.

I've modified my driving style, partly in response to fuel prices, partly as a result of thinking "If only I had a more economical diesel/faster petrol" and wanting to change car all the time, rather than giving the car a chance, I've got my car back to the 43 mpg from the last tank, 45 from the previous one, compared to the ~36mpg I was getting driving harder.

My driving style, though not overly aggressive, sounds like it was like yours and now I drive as WhiteTruckMan suggests. The result is that I've more than cancelled out the fuel price increases and am getting just over 500 miles from a 52 litre fill up, compared to barely scraping past 400 before the red light came on.
Petrol Consumption....AGAIN - Adam {P}
Thanks for the many more replies.

Firstly, I'm not overweight - or at least I don't think I am. I'm 16 1/2 stone but I'm 6ft 5 so not a lot I can do about that!

28mpg doesn't sound too bad really David. Thanks for working that out! I've used just over quarter of a tank with this new style so I'm seeing a few more miles to the gallon but I'll have to work out the proper figures later.

Watch this space.
--
Adam
Petrol Consumption....AGAIN - mjm
No, you're not overweight, just a foot too short! Low gears and high revs is the major use of fuel.
Petrol Consumption....AGAIN - PhilW
"I'm 16 1/2 stone but I'm 6ft 5"

Blimey, that's destroyed my image of you - like when you read a book and then they make a film of it using someone completely different from what you have imagined. Don't know why but I pictured you as about 6ft and 11 stone, fair haired etc. Mind you, I have a better image of your car - someone just down the road has just got a gold (beige?) booted Focus - am I closer with this image?
Picture of ND's goatee somewhere destroyed my image of him as a debonair, smart businessman! Won't tell you my image of Mark and Hugo but aren't Nowheels and Pologirl gorgeous!!
PS I'm a grey haired (well, blonde really) grumpy old git.
Petrol Consumption....AGAIN - Adam {P}
Gold...gold - It's GOLD!!! ;-)

What can I say? I'm big. Probably accounts for my lousy fuel consumption!!

I do have blonde hair though so that's something!
--
Adam
Petrol Consumption....AGAIN - Big Bad Dave
6ft 5 and 16 1/2 stone with blonde hair?

I know who you are. You?re He-man, master of the Universe!

By the power of Greyskull...
Petrol Consumption....AGAIN - Adam {P}
You've been eating too many red sweets today haven't you Dave?!

Too many E numbers ;-)
--
Adam
Petrol Consumption....AGAIN - Big Bad Dave
"You've been eating too many red sweets today haven't you Dave?!"

Yeah, cos you ate all the pies!
Petrol Consumption....AGAIN - PhilW
"He-man, master of the Universe!"

New image!! Not bad - but what about the beige Focus with a boot, what can I do about that!!??

Petrol Consumption....AGAIN - No Do$h
LOL....

::scrolls back up::

PhilW, see me after class.

Pleased to say that whilst the goatee remains, the beergut is waning fast. As for debonair businessman, I scrub-up pretty well if a decent suit is draped about my person. Or at least I think I do, I can't see people paying me as much as they do on the basis of my CV.
Petrol Consumption....AGAIN - BobbyG
Well going back to the fuel consumption topic, I'd just like to say I have had my diesel Saxo for 4 years now and have averaged 59.145 miles to the gallon! Yes I am a sad git who runs a spreadsheet for his fuel.
Currently doing a longer 100 mile round trip and getting 63mpg. Car is slow, rattly, noisy and pretty uncomfortable but hey, I can get over 600 miles out of a 45 litre tank!
Petrol Consumption....AGAIN - blue_haddock
I use a rover 100 diesel as a run around to keep my demo clean and respectable - i get about 55 to 60 out of it and thats driving everywhere foot to the board (you have to - it's the same 1.5 diesel as in BobbyG's saxo)
Petrol Consumption....AGAIN - frazerjp
Hey Adam, i get between 44-50 mpg in my Ford Ka with a mixture of roads, what i was taught to do was to reach cruising speed as soon as you can, if i was to take off at the lights in 30 mph limit when conditions allow it: i change into 2nd at 20 mph then at 30mph i block change from 2nd to 4th, not sure your Focus can do that dure to the different gearing, but then if you were to accelerate onto a motorway, my driving instructor said to stay in 3rd upto 60 mph then block change into 5th, you can save some fuel by less gear changing!!!
--
Its not what you drive, its how you drive it! :-)
Petrol Consumption....AGAIN - Adam {P}
Actually, DAVE! I've stopped eating pies now and have gone to...erm....McDonalds. ;-)

Anyway, frazerjp. 50mpg? You're just making me feel worse now! What I have noticed though, in 30mph limits, I've been sitting in 3rd a hell of a lot more because for the most part, they're on a very slight incline and to traverse them in 4th would make the engine labour too much. At 35 however, 4th is perfect for them.

I am interested to see the figures when I've done it though.
--
Adam
Petrol Consumption....AGAIN - machika
Are you sure you have got your figures right Adam? Even at todays prices, your £50 would equate to at least 12 gallons of petrol. If you are only getting 245 miles from this amount of petrol, there is something radically wrong.

It is none of my business but I couldn't have funded that kind of fuel consumption when I was a student. Come to think of it, I couldn't fund it now!
Petrol Consumption....AGAIN - Adam {P}
Well the trick is, when you put the petrol in, run off very quickly! Joking! Joking! I manage it...just but obviously I'd rather have to put less in!

I should point out that that £50 a week isn't from a full tank. I only ever put £10 or £20 in which usually puts a bit under half a tank in.

ALSO, I may have made a gross misjudgement when it comes to the distances to my Mum's work. A gross misjudgement of 8 miles. I forgot that I go a different way back for the fun roads and to miss the traffic out.

On just under half a tank now by the way. I did get quite impatient behind a knackered Tranny van before though and kind of....well - overtook him quickly on a perfectly straight, open and empty road. It was only about 5 seconds of foot to floor in 3rd though so hopefully I haven't screwed up the figures too much.
--
Adam
Petrol Consumption....AGAIN - machika
Ok then, let us know an accurate number of miles per tank, and what the tank holds. It doesn't matter how many times you fill it up, just how many miles per tank. I would have thought £50 was around a full tank at least?
Petrol Consumption....AGAIN - Adam {P}
£50 would fill the tank . I don't put the 50 in all at once - I never fill a tank until this experiement.

55 litres is popping into my head from somewhere for tank capacity. I shall check this and wait till I run out of juice for miles on each tank.

It's quite interesting actually - up to this point, I've just plonked the petrol in and never thought about it. Whether the findings will make me change my driving style, I don't know! But I want to see how much of a difference driving like I'm dead makes.
--
Adam
Petrol Consumption....AGAIN - mfarrow
£50 would fill the tank... 55 litres is popping into my head
from somewhere for tank capacity.


If this is true, you need to find yourself a new filling station mate! 91p a litre??
--------------
Mike Farrow
Petrol Consumption....AGAIN - Adam {P}
Can't be 55 litres. I never filled the car you see so I wouldn't be able to tell you the exact amount it cost to fill the tank. I was just working off 20 quid putting just under half in, another 20...you get the picture.

89p a litre I think....I'm pretty sure anyway!
--
Adam
Petrol Consumption....AGAIN - Car
Have looked at a back issue of what car, according to them the fuel capacity is 12.1 gallons which is equivilant to 55 litres.

Unfortunatley measuring fuel compsumption by using the guage will produce alarming mpg compsumption. Eg on my car the fuel light is meant to come on when I have used up 10.5 gallons left and on average this occurs after I have driven aprox 330 miles, so if I was going by the guage my mpg would be 31mpg but when I fill the tank up it will only take aprox 9.25 gallons making my mpg to be around 36 mpg.

Petrol Consumption....AGAIN - Adam {P}
That's interesting.

I must admit, I drive loads on the light. For example, if the light's on in the morning and it's just come on, I won't immediately go to get petrol. I've never run out yet so I'll have to check the manual to see how much reserve is left when the light illuminates.
--
Adam
Petrol Consumption....AGAIN - GrahamF1
Reserve (when light comes on) tends to be the last 10-12% or so of the overall capacity. So 4-8 litres, depending on your tank size.

Some very interesting points raised in this thread. Adski, your consumption is definitely way too high. Unless you've made some errors with your figures, or your driving style is aggressive beyond belief, then there is something wrong with your car.

I've never quite understood putting small amounts of fuel in the tank at a time. I appreciate there may be financial reasons, but these are usually pyschological ('it doesn't feel so painful if I don't spend so much in one go') rather than genuinely insurmountable. I buy all fuel on my credit card and pay the bill in full each month after I get paid. Filling up with fuel costs time (and fuel if you have to deviate from your usual route to do it), so I reason that it's best to do it as little as I have to - i.e. fill the tank each time and run it until almost empty.

Interesting points also about fuel consumption as related to throttle position / engine revs. On older engines I think it's simply related to throttle position - you push the pedal further down and the throttle butterfly(s) open(s) further and the inlet manifold vacuum sucks more fuel from the carburettor(s). Of course there is the potential for wasting lots of fuel here. On my Spitfire I only open the throttle gradually at first, and a bit more rapidly as the revs increase. If I were to plant my right foot on the floor at 1000 rpm, then the engine would simply suck in far more fuel from the carburettors than it is capable of burning at that sort of speed.

With modern fuel management systems, your control with the 'gas pedal' isn't quite so direct. Pressing it further down tells the system you want more revs, but the software won't generally allow the injectors to supply more fuel than the engine is capable of burning at that particular speed.

A very interesting thread...
Petrol Consumption....AGAIN - Altea Ego
"With modern fuel management systems, your control with the 'gas pedal' isn't quite so direct. Pressing it further down tells the system you want more revs, but the software won't generally allow the injectors to supply more fuel than the engine is capable of burning at that particular speed."

Which is why most modern cars return much better consumption figures then the old ones.

You still cant escape basic science tho. To accelerate a body requires effort, to accelerate that body faster requires more effort. To keep an already moving body moving requires much less affort. To stop a moving body requires throwing effort away somewhere

Effort = gas.
Petrol Consumption....AGAIN - GrahamF1
"Which is why most modern cars return much better consumption figures then the old ones."

Whilst I don't dispute this point, you can get excellent consumption from an older engine - it just requires a lot more skilled use of the throttle than a newer engine does.

You've nailed it with the effort/acceleration/momentum thing, RF. Momentum as we all know is the holy grail of truckers, and for a good reason. Too often though they can be seen prioritising it above keeping a safe distance from the vehicle in front!

To draw an example here, my girlfriend is on a week-long course in Cambridge this week and is doing the nightmare stretch of the A14 each day. She gets scared witless by how close the trucks sit to her rear bumper. Problem compounded by the fact that she's stubborn and refuses to let them bully her out of the way - I think she'd be better off with my approach of 'the guy is being an idiot, best defence is to be somewhere he's not'.
Petrol Consumption....AGAIN - Ex-Moderator
Does anybody know what fuel consumption I would have been getting from a MKIII Cortina 2.0 or a bog standard 1967 Mini 1000 ?

Petrol Consumption....AGAIN - bazza
Saddo that I am, still have the fuel records from my 1969 Mini 1000, about 40mpg average, worst high 30s best mid 40s. Interesting that my 1.6 Megane averages more than that now!
Petrol Consumption....AGAIN - mfarrow
Adam, my mate had a 1.4 Xsara (I know, we tried to stop him), which had high fuel consumption. Tell-tale signs in this were engine pinking under load and oil smelling of petrol! Two things I think you should check.
--------------
Mike Farrow
Petrol Consumption....AGAIN - v8man
All this talk about 50mpg is making me go all funny. My Range Rover 4.2 does 13mpg! I try not to work it out if I can - it's too depressing.
--
\"Nothing less than 8 cylinders will do\"
Petrol Consumption....AGAIN - Adam {P}
Mike,

the oil doesn't smell of petrol, nor does the car pink. It drives perfectly. If anything, it seems more responsive than ever!

Graham, you will rarely find over half a tank of petrol in either mine or my Dad's car. I've said before that I thought this was the norm but it seems we're just odd. We always have put 20 quid in and for the most part I always will. The exceptions are if we're going on a very long journey however.

95% of the time, I fill up at the petrol station I pass every day so no wasted petrol. Plus the fact, I'd be carrying half the weight other people do - that's negligable I know it would offset any extra fuel costs to fill up.

In any event, I've gone just under half a tank now.
--
Adam
Petrol Consumption....AGAIN - JH
Adam,
good luck with the experiment. I did something similar many years ago and discovered two things:
it was BORING
it made no difference to the fuel consumption whatsoever, which was quite a shock.

You're right about the fast car phase prior to diesels. I now drive a diesel, having given permission to my wife to shoot me if I ever bought one a few years previously. My excuse it, it don't half go. I'm now trying to convince myself that a big petrol engine would give the sort of mid range performance that the diesel gives and do I cover enough miles pa that the increased fuel consumption would matter v the higher purchase price ?

Good luck,
John
Petrol Consumption....AGAIN - machika
In any event, I've gone just under half a tank now.

>>

So did you fill it up to start with? You won't get any accurate figures unless you do.

Commenting on fuel consumption from older cars, I used to get about 33 mpg from an NSU 1000, which I owned for many years, and about the same from a 1300 Marina (I didn't own it, it a company car). The Marina was replaced with an Ital, which did nearer to 40 mpg. These cars were set to run much leaner and, unforturately, it caused it to almost stall every time I moved off from a standing start.

I then progressed to two 309 1300s, which returned almost identical mpg, at around 40 mpg. Following those was a ZX, which easily achieved 40 mpg. Only the ZX had fuel injection, of course.

My driving style hasn't changed a great deal in 35 years.
Petrol Consumption....AGAIN - Adam {P}
JH - it is boring!!! I'm hoping I don't see that much of a difference so I can justify NOT going that slow!

Machika, I did fill the tank for this experiment.
--
Adam
Petrol Consumption....AGAIN - cjehuk
Adam,

It's not a focus, but driving within the limits and gentle acceleration does make a difference... for my Audi A3:

Driven hard: 40mpg
Average Tank: 49mpg
Good tank: 56mpg (no limits broken but still some hard acceleration)

Best tank ever: 66mpg, but that was mainly distance driving and I didn't exceed 70mph at all.

Chris
Petrol Consumption....AGAIN - Adam {P}
66mpg Chris is amazing!

However, the results are in.

Having worked it out, I can now tell you, driven completely within the limit on all roads (yes - all of them!) I have returned 26.11mpg.

That being said, the fact my back brakes were half on apparently (fixed along with the coil pack) may have altered the results which is why I am going to conduct the experiment again this week. If I get over 30, I'll be happy.

Thanks for all of your comments. I must say though, I don't like all this obeying the law malarkey! ;-)

30mpg here I come!
--
Adam
Petrol Consumption....AGAIN - Adam {P}
Oh - that's not taking it over 3,000 revs once, and effectively half the engine power for one day (knackered coil pack!).

Also, I stayed on the inside lane mostly - driving at around 65mph when I could which was boring, but in the name of science, I had to!

All of this had led me to draw the conclusion that I must have been getting just under 20mph before this.

An interesting experiement anyway.
--
Adam
Petrol Consumption....AGAIN - VTiredeyes
20mpg you mean?
Petrol Consumption....AGAIN - VTiredeyes
try doing 56mph the week after, i think you will see even more of an improvement.
its good fun tho, huh?
think of the saving of petrol, then just blast it all away on a friday night !
and it wont cost you a penny more!
Petrol Consumption....AGAIN - Adam {P}
Exactly VTiredeye - you're on the same wavelength!

And yes I did mean mph. Damn keyboards!
--
Adam
Petrol Consumption....AGAIN - Adam {P}
and I meant VTiredeyeS!
--
Adam
Petrol Consumption....AGAIN - y2k+4
What are the boundaries of the experiment? Windows up/down? A/C on? Radio? Heater? All will affect the consumption...;-) gd luck tho...
Petrol Consumption....AGAIN - machika
Having worked it out, I can now tell you, driven completely
within the limit on all roads (yes - all of them!)
I have returned 26.11mpg.
That being said, the fact my back brakes were half on
apparently (fixed along with the coil pack) may have altered the
results which is why I am going to conduct the experiment
again this week. If I get over 30, I'll be happy.


You should be unhappy if you don't get over thirty.

Petrol Consumption....AGAIN - Adam {P}
I forgot to update this.

After another week of deathly sedate driving, the result is;

28.64mpg



Having become so bored I'm going back to "normal" driving. It will be interesting to see how much a difference it makes.
--
Adam
Petrol Consumption....AGAIN - Adam {P}
y2k+4,

I could have swore I replied to you ages ago but;

A/C off. Windows down for around town - up on the motorway so shouldn't be too bad.
--
Adam
Petrol Consumption....AGAIN - machika
Something is amiss somewhere, if that is all you are getting with fairly sedate driving.
Petrol Consumption....AGAIN - Adam {P}
I did overtake someone doing 30 on an NSL road because it was taking the mick. But that was a few seconds hard acceleration in 2nd. Not enough to skew the results that much surely.

Are you sure 28mpg is bad? Looking on t'internet, people say the 1.8 is notoriously thirsty. I can live with sub 30mpg. When I get a nice V6 or V8, it won't hit me so hard!
--
Adam
Petrol Consumption....AGAIN - machika
It doesn't sound very good to me, when the new 2.0 litre Focus is given a combined figure of nearly 40 mpg in the Car-by-Car Breakdown.

What are the official figures from Ford for the old 1.8 Focus?
Petrol Consumption....AGAIN - Adam {P}
I don't know what the official figures are for mine but I'm pretty sure you wouldn't get 4ompg out of a 2.0 Focus however you drove it.
--
Adam
Petrol Consumption....AGAIN - tyro
If What Car? is to be believed, combined figure should be 37.7, urban figure should be 27.4.
Petrol Consumption....AGAIN - Adam {P}
For mine or the new 2.0?
--
Adam
Petrol Consumption....AGAIN - machika
Just looked on Autobytel and the figures given for the 1.8 Mondeo (125 bhp) are:

Combined - 37.2

Urban - 25.7
Petrol Consumption....AGAIN - Adam {P}
That does surprise me. I'd have thought a car as heavy as the Mondeo would have lowered those figures quite a bit.
--
Adam
Petrol Consumption....AGAIN - machika
Also on Autobytel, for the new Focus 2.0 litre

Combined - 39.8

Urban - 28.8
Petrol Consumption....AGAIN - tyro
For mine or the new 2.0?


Yours
Petrol Consumption....AGAIN - Adam {P}
Surely that's in keeping with what I've returned though?

Usually built up areas - the odd 40mph road, a 70mph dual carriageway for about 1 mile and a 10 mile motorway blast every day.
--
Adam
Petrol Consumption....AGAIN - tyro
Surely that's in keeping with what I've returned though?
Usually built up areas - the odd 40mph road, a 70mph
dual carriageway for about 1 mile and a 10 mile motorway
blast every day.


Exactly. With your driving routine, it would be unrealistic to expect anything more than the quoted urban petrol consumption figure.
Petrol Consumption....AGAIN - machika
Exactly. With your driving routine, it would be unrealistic to
expect anything more than the quoted urban petrol consumption figure.


With that mix of driving, you should be getting better than urban cylce figures. It is very similar to the mix of motoring I have mostly done for years with our Xantia and that never returns less than 40 mpg (remember, it is old diesel technology). I would expect you to get low thirties at least.
Petrol Consumption....AGAIN - mfarrow
I don't know what the official figures are for mine


This tells you enough:

www.vcacarfueldata.org.uk/search/vehicleDetails.as...1

The 27.7 mpg figure is for cold running, remember. Bit low to me.

--------------
Mike Farrow
Petrol Consumption....AGAIN - Dude - {P}
>>Are you sure 28mpg is bad? Looking on t'internet, people say the 1.8 is notoriously thirsty.>>

That is absolutely appalling - my son`s BMW 530i Sport manual is averaging 34 mpg overall and on motorway cruise at 75 mph regularly returns 38 mpg. I know this is pathetic besides some of the diesel figures quoted earlier in this thread, but for a 3 litre petrol engine, with superb performance when needed, IMHO is excellent.
Petrol Consumption....AGAIN - machika
Yes, I would agree, but BMW engines are known to be frugal.
Petrol Consumption....AGAIN - machika
The figures aren't much worse for the 2.0 Mondeo

Combined - 36.2

Urban - 25.2
Petrol Consumption....AGAIN - Adam {P}
You're right. They're not much worse.

God help me if I had an ST24...or even a 3.0 ST220!

Still, at least I don't have a V8 Rangie...(sorry v8man!)
--
Adam
Petrol Consumption....AGAIN - blue_haddock
The Landie that i offroad in has a 3.5V8 Efi in it with an auto box - during normal driving it will average about 16-18mpg. This is in a couple of tons of Landrover 90 which has the aerodynamics of a breeze block and permanent 4wd.

If you are only getting 10mpg more in your focus there is either something up with the car or something up with the way you drive it. In my old Peugeot 309 Gti i would get about 30mpg out of that and i drove that VERY hard.
Petrol Consumption....AGAIN - Adam {P}
34mpg??? That is amazing on a 530. That'd be good on a 320!

I can't drive any slower as there's no point. I've driven pretty much at the limit and never over, changed gears before 3,000 revs, never laboured the engine, never had the aircon on or anything.

28mpg doesn't sound that ridiculous to me but compared to 34 for a 530 is concerning me somewhat.
--
Adam
Petrol Consumption....AGAIN - David Horn
I think there's something up with your car. My brother has a 1.6 Megane (2003) and that returns high 30's -> low 40's on a combined journey and is in fact now cheaper to run than my 1.9 diesel Xsara, which returns 44-50mpg.
Petrol Consumption....AGAIN - Adam {P}
The face that a V8 Landie isn't too far away from my consumption is worrying. Also, I never knew the 1.6 Megane was so economical. My Mum wants one but we don't like her to be so independent - better make sure she never finds out about the consumption ;-)

However, I was speaking to someone last night who had a 2.0 Zetec as a company car a while back and didn't think 28mpg was too bad. He said he seemed to be always filling up. I'm not quite sure whether I'd be happier if there was no problem - my car was just thirsty or that there was a problem which could be fixed thus solving the problem!

Thanks for all your help guys
--
Adam
Petrol Consumption....AGAIN - Alfafan {P}
I've run my Alfa 155 2 litre twin-spark for nearly 2 years. A fair mix of motoring, 20 mile commutes on fast A roads, some urban and I don't hang about. I keep a meticulous record of consumption, brim to brim every time.

Cumulative average to date is 32.5 mpg, worst tank 27.0, best 37.5.

I'd say there's something wrong with your car.
Petrol Consumption....AGAIN - andyconda
I'd agree that there must be something wrong with your Focus, or with the way that you're calculating mpg.

I used to get 35-40mpg out of my MX5 and my Golf 1.8T, and this weekend I got 40mpg out of my Fiesta 1.25 on a trip down to Bournemouth (50/50 split between motorway and twisty A-roads, carrying two heavy passengers and luggage).
Petrol Consumption....AGAIN - TimW
Why don't you just take it to a rolling road/tune up place?

Sounds like a duff sensor to me.
Petrol Consumption....AGAIN - chris_w
As I said earlier on this thread, my old 1.8 Focus (2001) used to return about 26 - 28mpg. It was driven fairly enthusiastically, but even when I was on long journeys it was still pretty poor. So I don't know if there's much wrong.

Now got an A4 1.8T and am getting about 30 to the gallon, only difference is the tank is bigger so I feel a bit poorer each time I fill up (I know that I'm not poorer, just feel it!)
Petrol Consumption....AGAIN - mfarrow
I understand the 2.0 litre is particularly thirsty, but I don't know about the 1.8.

How did the last MoT test go? An MoT test would have spotted signs such as overfuelling via excessively high HC output, and any brake binding problems.

--------------
Mike Farrow
Petrol Consumption....AGAIN - Stargazer {P}
Adam,

Just for comparison, Volvo V40 1.8XS (standard not the GDi engine)
weights approx 1400Kg, estate version. Not a light car for its size. W (2000) reg.

Commuting/shopping general use with rural B roads, some A roads some traffic around Oxford. Some hard accelerating, generally 2000-3500 rpm with excursions to 4000 rpm. average 33mpg.
Very very few journeys less than 7 miles each way.

Long journeys steady 70 on motorways typically 37mpg, can be upto 43mpg for long A road journeys.

Worst tank 28mpg, Best tank 46mpg

So heavier car with same size engine.

StarGazer
Petrol Consumption....AGAIN - Leon on Derv
Adam,

I haven;t taken time to read all hundred odd posts in the thread but I do recall reading the original postings.

Have you had your MAF checked /replaced? Mine hadn;t totally failed but was not working correctly, gave rubbish MPG on the Leon - won't always show on diagnostics.

My Impreza returns similar mileage to your motor when you drive it easy.... Its a thirsty 2L 280BHP brute of a thing!

Have you tried fuel with a higher RON - Optimax or the new Tesco 99 Ron stuff. Might lift the MPG a bit for a few extra pennies a litre???

Leon
Petrol Consumption....AGAIN - SlightlyFatRep
I would agree with other posts that there is something not quite right with the car.

I had the 1.8 16v in my company Escort complete with A/C which was on most of the time. This car was with 105ps rather than the 115ps (ps = near-enough bhp if you like) you are probably enjoying. As far as I am aware the higher powered engine was more efficient = better mpg (I stand to be corrected........)

I thrashed the life out of it from 1997 (100 miles on the clock) to 2000 (87,000 miles) with very mixed motoring (heavy congested towns, a bit of M/way, etc).

I never had less than 33mpg from a full tank, even on days in West Wales along the coast heading South to North (ah, wonderful driving roads, even in an Escort!) pretty much foot-to-the-floor.

My next car was a 2.0 Mondeo Estate Ghia X (so very heavy with goodies). Pretty much the same driving style and average to a tank was 33 mpg. Only got into the high 20's with 100% town driving with no open roads at all.


I now have a Volvo S60 Diesel D5 and on the first 2,000 miles have averaged 43.4mpg, but that is using the 'running-in' techniques recommended to me from an earlier post on this site which I have enjoyed following.

It is interesting to slow down a bit and see what difference it make to mpg (got the Escort and Mondeo up to mid-40's on very gentle weeks) but I still cannot resist that loud pedal on the open road (although within limits of course - I strictly adhere to all limits but M-Way, and even then no more than 82mph.



Petrol Consumption....AGAIN - madf
I keep a record of all miles and fuel and my 2001 1.6 Fiesta (same engine as Focus) has improved from 37mpg overall to 39 as I have run it in - now just under 20k miles.

I regularly use Shell (standard) or Texaco petrol. I find supermarket petrol gives 2-3 mpg less. (all based on brim to brim and recorded mileage).

I accelerate briskly (not hard) and use 5th gear whenever I can - it will pull from c 27mph.
I rev to 6,000rpm at least once a week and travel at 75mph on motorways - no faster. Keeps the engine clear of gunge and prevents combustion chambers fouling up.

In town I try to anticipate holdups and will slow down before I join a queue if there is a chance it will start moving again before I stop.

And never acclerate hard up hills: that's the best way to waste fuel....

madf


Petrol Consumption....AGAIN - tyro
And never acclerate hard up hills: that's the best way to
waste fuel....


Interesting comment. I've been wondering what the best way of taking hills is. My usual method is to try to get up some speed (not always possible, of course), and then take them in 5th gear if possible, and if not, 4th (& if that's not possible, 3rd.) Would I be better opting for a low gear, and just going up them slowly?
Petrol Consumption....AGAIN - Xileno {P}
My policy is to be in the highest gear possible without labouring the engine.
Petrol Consumption....AGAIN - tyro
My policy is to be in the highest gear possible without
labouring the engine.


Thanks. That raises another question, but I'll post elsewhere so as not to get this thread off the track!
Petrol Consumption....AGAIN - JH
28 !! I had a 2 litre Mondeo hire car and got the best part of 40mpg out of it. And I wasn't hanging about.

John
Petrol Consumption....AGAIN - Adam {P}
Sorry - I read all of these and cried into a bottle of Jack's finest.

On a serious note, you're all crying out something's wrong but if you give me until Saturday, I can give you the reading I get when driving....enthusiastically.

There is a really, really steep hill that must destroy fuel consumption. Unless you hit it doing 30-35 you'll need second. AS it is, I need third to get up to the very top as there's a bend and those ridiculous chichanes on the "peak" so 4th would leave me in the middle of nowhere with no place to go.

I'm quite interested to see what my "normal" driving figures will be.


--
Adam
Petrol Consumption....AGAIN - tyro
Frank???
Petrol Consumption....AGAIN - blue_haddock
Frank???


Yeah i was wondering too
Petrol Consumption....AGAIN - L'escargot
>> Frank???
>>
Yeah i was wondering too


He's probably only being perfectly frank!
--
L\'escargot by name, but not by nature.
Petrol Consumption....AGAIN - commerdriver
He's probably hiding from Nowheels
Petrol Consumption....AGAIN - Adam {P}
He's probably hiding from Nowheels<<


How did you guess?

Seriously though, it was my attempt at humour. Let that be a lesson to you all - don't take Wit Lessons off Alan ;-)
--
Adam
Petrol Consumption....AGAIN - No Do$h
>> He's probably hiding from Nowheels<<
How did you guess?
Seriously though, it was my attempt at humour. Let that be
a lesson to you all - don't take Wit Lessons off
Alan ;-)
--
Adam


I hadn't realised you were attending the lectures.
Petrol Consumption....AGAIN - Ex-Moderator
Surprising really, since only the other day I overheard someone commenting that Alan was a shining wit. I might have misheard, I suppose.
 

Value my car