I felt really chilled at the start of last week, and consequently for the first couple of days my driving style was different. I was sticking to 70 on the motorway and not pushing it to 80, and was accelerating gently from standstill and also when picking up speed. After a couple of days I noticed that there was a marked increase in my petrol consumption, so I carried on with the same style.
When I filled the tank yesterday, just after the warning light came on, I had done 370 miles, compared to the usual 300.
I average 30,000 per year, so instead of 100 refuelings, at this rate I would only need 81, and at £40 per tank, that's almost £800 worth of savings, and it's only added a few minutes onto my daily commute.
This week I'm going to attempt the 400 mile barrier. Drove to work today and didnt enter lane 3 at all, instead choosing to mix it with lorries (when the gap was big enough) and stick around the 60 mph mark.
Sadly I know that this attitude won't last :o(
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With you all the way here. So many drivers ignore the large difference between the published figures for '56mph' and '75mph'. But I think your comsumption decreased, not increased? 'Improved', perhaps?
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Agree, but are the published fuel consumption figures much of a help?....we now have the urban and extra urban cycles and the combined value...neither of which are much use for a steady
speed motorway journey.
I preferred the older system of mpg (or L//100km) for 30mph, 56mph and 75mph. But I havent seen these recently.
As a case in point, my 1986 C reg Mk2 Fiesta had very good economy
(45-47mpg) if I stayed between 65-70mph on the durham/bristol/durham round trip which was all dual carriageway or m-way. But if I used the loud pedal a little, say 70-75 the fuel consumption dropped to below 35mpg and I was lucky to make the trip each way without filling up.
regards
Ian
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pdc- agree with the reduction in speed being beneficial, but I'm not sure about the 'accelerating gently from standstill'. Using the digital readout on my 1.0 Yaris, it looks like accelerating briskly (a relative term) then laying off the pedal ASAP is better than a slow build-up.
I would be interested to see if your consumption changed either way if you carried on keeping your speed down but accelerated as normal.
John
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totally agree, i average 35.5 in audi a6 and sometimes get 38mpg if i drive really carefully (60mph on motorway). its amazing the difference careful driving makes and u dont save that much more on time. im not some old man but do get fed up with sticking petrol in the tank and if you can save yourself a bob or two then why not
the fastest lane of the motorway is usually the middle lane as its moving at a constant rate, where the fast lane is constant stop start.
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I remember years ago seeing research from BMW (I think) that reckoned the most efficient/economical style of driving involved "brisk" (not full power) acceleraton to a higher-gear cruising speed, rather then being in lower gears for longer.
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John M raises an interesting point. Is it better to accelerate slowly to one's desired speed or to do so quickly?
This is partly about engine efficiency (more efficient at wider throttle openings? But then that depends on the power and torque curves of individual engines) and partly about energy demands - as a basic principle it takes more energy to accelerate 1.25 tonnes of car to 60mph in 10 secs than it does in 20sec. But having done it in 10sec the car uses less fuel maintaining that speed up to the point where the slower accelerating one reaches 60mph.
There's some swings/roundabouts stuff here. Maxy's rules of fuel maximisation are:
- Accelerate fairly gently; change up at 2500-3000 rpm
- Once cruising try and avoid slowing down, even for corners (motoring has to be fun)
- Think ahead and use engine braking (I hate brake dust on my clean alloys)
- Avoid lifting on and off the throttle; keep pressure as even as possible
- 75mph or so on motorways etc: gets me there quick enough and avoids attentions of plod.
Essentially I only get overtaken on motorways, and by mad PFDs on other roads, on which I overtake whenever I safely can. Without stop-start town journeys get close-ish to the official 75 consumption.
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"John M raises an interesting point. Is it better to accelerate slowly to one's desired speed or to do so quickly? "
see www.telegraph.co.uk/news/main.jhtml?xml=%2Fnews%2F...l
and thread www.honestjohn.co.uk/forum/post/index.htm?t=9008&v...f
In summary, you should accelerate at max torque revs for your car. In my case, that's at 3,200 revs, which makes it take off pretty damn quick. The reason it works is that the increase in fuel consumption during the acceleration is more than offset by the greater time then spent at a constant speed.
In the case of this thread, the improvement in consumption is probably due to the lower max speed being used; above a threshold, slowing down will always reduce consumption. Don't know what the threshold is, though I do remember the Metro being announced as having done 85mpg at a constant 30mph, so it's probably below 30mph.
56mph is chosen as it's meant to be a reasonable trade off between speed and consumption (though 56 on a motorway these days = mobile roadblock)
V
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I know it's not up there with the big boys but I own a Fiesta which, around town is cracking on petrol. I tried pdc's method but when I was getting bored I decided to drive quicker :-) (Sorry) One thing though - consumption on the car at 70 ish is pretty poor - I'm guessing because they're not designed for motorway driving and so, scream revs wise at that speed.
Otherwise an absolutely cracking car.
--
"Ah...beer - my only weakness - my achilles heel if you will"
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Well, I'm continuing to experiement away and am bearing in mind some of the points raised here. I'm also relying solely on the heated seats to keep me warm, so as to ensure that the climate control isn't having an effect on the consumption.
With the old style of driving the onboard computer used to record about 28mpg for the daily commute. I've now got it to 34.5 mpg. that's 12 miles motorway and 3 of a-roads each way.
going out with the attitude of going with the slow flow has also lead to a reduction of stress during the journey.
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Ah, mishtake!!
In my post above, I meant I get close to the 56 mph official figure. Bet you're all impressed now.
Well OK...
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But what did you do to get so chilled out? Advice on that point would help many of us!
Agreed that the difference is more than you usually think. I left a distant office one day for a 90 mile drive home with the trip computer predicting a 95 mile range based on recent driving styles. I decided to stop to fill up but discovered that the wallet was in the other coat... So I decided to go for it and drive for economy.
About 30 miles into the journey the trip computer was saying 140 miles to go...
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In my experience, for 90% of my journeys I lose very little time by travelling at 65mph instead of 75mph. Certainly the matter of a few minutes saved are not worth the extra cost of the fuel burnt. (25k miles per annum, motorways and A roads.)
I find travelling at 65mph makes for a much smoother journey, allows me to maintain a much more consistent throttle opening, and as previously mentioned, reduces stress significantly.
Ed.
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My diesel automatic Terrano can manage 30 mpg if I cruise strictly at 70mph but above that the comsumption rises steeply. It is probably down to the brick-like aerodynamics.
However I often see similar off-roaders being pushed along at 80mph+. Who is paying for their fuel? Is it the case that a lot of drivers just don't bother about fuel economy?
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Is it the case that a lot of drivers just don't bother about fuel economy?
Yes. At least, I often can't see any other reason.
No doubt they whinge about the poor consumption and buy magnets to make things better.
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Since most 4x4s look like fridges, perhaps magnets will enhance them!
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Well I managed 396.2 miles before the refuel warning light came on. It usually comes on at around the 300 mile mark. Managed to get an average consumption of 41mpg (according to the computer) at the weekend, a figure never before seen on the display!!!
Hope to pass the 400 limit this week.
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That's not bad, pdc. Just think what you might achieve if you left the seats switched off! :o)
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pdc,
Did you manage the 400 mile barrier?
Ian L.
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