Benefits of Optimax... - kennybase
Morning all,

I've just got back from a long driving weekend through France, where, in my wisdom, I decided to buy some petrol before I left (ferry was getting in at 7am - I just wanted to drive when I was there and not spend/waste time looking for a garage). I therefore went to the nearest Shell garage, and decided to splash out on some of there OPTIMAX fuel that they say will improve the performance of my car. I took that to mean better fuel economy - perfect for what I needed. Anyway, fill up to the brim and off I went to the ferry. Arrive at my desitination about 400miles into France, (all motorway miles) tank in pratically empty - what a good job I used the Optimax I thought! Anyway, came home yesterday, filled up at the local Geant Casino (supermarket) and put in some of the Unleaded 98 fuel at about .98Euro/l. Made it home last night with at least 25% of the tank left! Only difference on the drive back was that the first 40miles were taken at about 50km/h not 130km/h due to the sudden snow storm and lack of gritted motorway! (not a plesant experience I can tell you!) Once through the snow it was back up to 130kmh / 4000rpm in my VW Polo 1.6CL (100bhp) and the fuel needle went down a lot slower!

Am I being conned into thinking that this Optimax will give me better economy or do they actually mean that performance will just be better acceleration etc - which for a motorway journey isn't really that important!
Benefits of Optimax... - Sooty Tailpipes
You need to take into account your height above sea level at both ends of the journey. Driving to the coast, I would expect it to be as low as it will go, which could account for the lower fuel consumption. ie downhill vs uphill.
Benefits of Optimax... - Vin {P}
I can only give one man's experience.

I keep accurate mpg figures for my Omega. I run on Tesco fuel, except for a while last year when I ran it on Optimax - there was no discernible difference. Before anyone queries, the driving mix was the same for the Optimax period.

It's possible that more usage might clean out the engine in some miraculous way and give me more mpg after a few more tanks. Additionally, it might just be that my car is suited to supermarket petrol.

You'll hear a lot of twaddle about how a specialist petrol retailer knows more about additives, etc, but I think that nowadays supermarkets are pretty much major retailers of petrol, so are well aware of what's involved. Also, the days when supermarket petrol was 5p per litre cheaper have gone, so basic economics suggests there's probably not much difference these days in the raw materials cost.

I've also repeatedly asked on this site if anyone has ever seen a scientific (rather than anecdotal) comparison of different petrols. Deafening silence was the result. It seems strange that something that is a major part of many households' expenses seems to have bypassed the good folk at "Which", etc.

Benefits of Optimax... - kennybase
Thanks for the replies.

I did think that maybe it was doing good for my engine, and that the real benefits would be seen after a few tankfuls - but at 81p/l its not something I really want to be trying out.

I've got a Chemistry degree - maybe now would be a good time to use some of the vast useless information that was drummed into me and actually do some comparisons :-) where did I leave my white coat.... ;-)

Benefits of Optimax... - teabelly
Maybe it is something that backroomers with regular driving mixes could do? Also anyone with access to a rolling road could do something similar and compensate for temperature changes and wind resistance. I reckon we would have to have at least tens of people doing this, preferably a few hundred. But there is the problem of different sources of petrol and whether you would have to fill up in the same place and at the same pump (differently sloping forecourts could seriously mess up the results). I think it would also have to be averaged over a seriously long time as I know I wouldn't be able to accelerate in the same way doing the same journey on different occasions. Traffic lights would also mess things up depending on whether you stopped or went through.

I know evo magazine ran some of their cars on optimax and they took pictures of the before and after of the engine innards. The optimax effect looked as though the insides had been scrubbed and polished.

Benefits of Optimax... - Honestjohn
Around a dozen Telegraph readers have sent comprehensive graphs showing how Optimax not only gives them better economy but actually takes them further per £. Dozens of other Telegraph readers whose cars weren't running properly on supermarket petrol switched to Optimax and solved their problems. I use it in my petrol cars. Towards the end of its time with me my Leon 20VT was averaging 35mpg, and our old 2.0 Mondeo, four up with their luggage managed a 300 mile journey, 60 miles of which was cross-country and through towns, in 4 hours and at 40mpg. Average 75mph and 40mpg is better than a lot of diesels.

Benefits of Optimax... - patently
I try to use Optimax exclusively for my BMW 530i, after deciding to test it properly. The 5 has an on-board average fuel consumption meter, so I alternated between Optimax and standard 98 RON for a while, resetting the fuel consumption on each refill.

I looked (hard) for a performance difference (tough, but someone has to) but frankly couldn't see any hard evidence. There is maybe a subjective feeling that the car is more willing to go, but I can't really say either way.

What I can say is that the fuel consumption was consistently 2-4 mpg better, averaged over months not days. The 530 is a bit thirsty, so an improvement from about 25 to about 28 actually make Optimax the cheapest fuel I can buy.
Optimax...I pick up the gauntlet - Vin {P}
OK, I'll run my Omega exclusively on Optimax for the next couple of months - I'm prepared to risk my own hard-earned in the search for truth for HJ's website.

I'll tell you all what happens in February. And believe me, if it's cheaper, I'll carry on using it.

Optimax...I pick up the gauntlet - GrumpyOldGit
I tried several tankfuls to give Optimax a chance but saw only one difference - my car did not start quite as well with a hot engine. No improvement to mpg or running that I could see.

I'm told that if your car has a knock sensor it can take advantage of Optimax so there could be a performance improvement. There's not much difference between Optimax or Ultimate and ordinary Super Unleaded apart from the added detergents. Both Optimax and Ultimate may clean your engine with prolonged use. It is suspected that both cause more polution than 'normal' petrol.

Supermarket petrol comes from the same few refineries as branded petrol. The difference is the additives that are mixed in the tanker. Texaco apparently use the same detergents as Shell and BP without the added cost.
Optimax...I pick up the gauntlet - scotty
Vin - that's incredibly philanthropic of you ;-)

Maybe it's Omega thing, but when I tried Optimax in my 2.5V6 there was no discernable difference (neither perform nor mpg) from Tesco's unleaded.
Optimax...I pick up the gauntlet - Honestjohn
Grumpy old git is completely wrong in what he says. BP Ultimate only claims to be 97 Ron and probably averages 97.1 or 97.2 Ron like other Superunleaded. Shell Optimax is independently measured (by Millers Oils) at an average 98.6 Ron. That makes it the highest octane petrol you can get in the UK and explains the performance improvement. The quality and quantity of detergents make the most of this by keeping the fuel system clean, as they do in Shell Premium and Texaco petrol.

Benefits of Optimax... - carlh
I started using Optimax in my Golf a few months ago. VW told me that it could run on Optimax but would give no improvement in performance (which would have been useful in a 2.0 115bhp GTI !). It's true that I have not really seen a performance improvement, but, after three or four fills, I am getting around a 3 mpg consumption improvement. As someone else has mentioned though, your car does need to have an adjustable (manual or automatic) knock sensor to take advantage of any benefit. For me, the main benefit is that I know that I am using a decent quality fuel.
Benefits of Optimax... - Aprilia
I am always surprised about people's misunderstanding and misconceptions of what 'Octane Rating' is all about. So many people equate a higher octance rating with 'more power'.

In the late 1980's I was, for a period, put in charge of an engine test lab. Lots of different work was going on, but one project was for a major petrol company doing research into fuel quality and octane rating. Since I was supposed to be in charge I decided to learn a bit about fuel - I can still remember some of it to this day!

Basically there are two methods of measuring OR - Research Octance Number (RON) and Motor Octane Number (MON). These numbers are never the same since MON is measured under more severe (and realisitic) conditions. MON is always lower than RON (RON is quoted on the pumps!). There is also something called 'fuel sensitivity' which is basically RON-MON - and this varies with the source of the crude oil, but typically is somewhere in the range 5-10.

Anyway, to cut a long story short, RON and MON are measured in single cylinder 'research engines' run at constant speed, wide open throttle and fixed spark timing. They have little to do with what you experience on the road and do not necessarily predict how the fuel will behave in real car engine. In a real car engine you need the 'Road Octane Number':

Road ON = a.RON+b.MON+c

Typcally a, b and c are somewhere around 0.5, but can be different for different fuels.

Thus quoting a fuel with RON value of 97 and comparing with a fuel of RON value 98 is meaningless. The 97RON fuel could easily have a Road ON higher than the 98RON fuel - depending on the source of the crude and the particular blend of antiknock additives used.

Another factor is that combustion chamber build-up can have a big impact on engine knock characteristics. I know from engine test work that as carbon builds up, the end-gas temperatures increase and so the knock problem becomes worse. Typically, engine deposits stabilise at around 10-20k miles from new; the engines' octane requirement will increase by typically 5 ON's over and above a new engine, but the range can be anything from 1 to 15 ON's. It depends on the engine because its all about the heat-transfer characterisitics of the combustion chamber wall.

In short, trying to determine whether Optimax gives more power and/or better antiknock characteristics than other fuels would be one of the labours of Hercules. It would need to be done in very carefully controlled conditions with very precisely matched angines and driving conditions.
My guess is that the characteristics of Optimax itself varies thoughout the year as the refineries take in different shipments of crude from different sources.
I would be inclined to keep my money in my pocket and buy the cheapest fuel that meets the British and European standards - which means anything sold on a UK forecourt.
Benefits of Optimax... - Wilco {P}
Blimey. Never knew there was so much to petrol.

On a totally subjective note, I'm convinced that my lawnmower cut the grass better when running on Optimax.
Benefits of Optimax... - M.M
>>On a totally subjective note, I'm convinced that my lawnmower cut the grass better when running on Optimax.

Subjective? That's pretty conclusive proof. And did you notice less weeds in your borders...there you are then!

Benefits of Optimax... - GrumpyOldGit
>>..Grumpy old git is completely wrong in what he says.

HJ, that seems a bit harsh. The only point you actually pick me up on is over a difference of 1.5 RON. Hardly 'completely'.

After reading Aprilia's comments my post doesn't seem to be very far out.
Benefits of Optimax... - Honestjohn
While I always respect what Aprilia has to say, that doesn't mean he is always right, you grumpy old git. As I wrote before, Optimax has fixed problems with a lot of Telegraph readers cars previously run on supermarket fuel, lots of readers have proved an economy benefit in miles per £, and so have I. You could say we are all imagininig it, like people did with fuel tank and fuel line catalysts. But a 75mph average over 300 miles, 60 miles of which were ordinary roads and towns, at 40mpg is pretty good to me from a 2.0 litre petrol engined car. Certainly a lot better than most diesels on that same trip.

Benefits of Optimax... - Aprilia
While I always respect what Aprilia has to say, that doesn't
mean he is always right, you grumpy old git. As I
wrote before, Optimax has fixed problems with a lot of Telegraph
readers cars previously run on supermarket fuel, lots of readers have
proved an economy benefit in miles per £, and so have
I. You could say we are all imagininig it, like people
did with fuel tank and fuel line catalysts. But a 75mph
average over 300 miles, 60 miles of which were ordinary roads
and towns, at 40mpg is pretty good to me from a
2.0 litre petrol engined car. Certainly a lot better than most
diesels on that same trip.

I'm not saying Optimax isn't a good fuel; I was saying that a 1 point increase in RON is neither here nor there.

I am very dubious when people claim that *any* petrol is responsible for a mpg increase from 25mpg to 28mpg. That's about a 12% increase and it is very difficult to imagine how that could come about. If one looks at *all* the gasoline fuel compositions on sale around the world the range of heat values varies only between 44 - 47MJ/kg (megajoules of energy per kg mass of fuel) - that's a variation of only 9% from 'best' to 'worst'. If Optimax is indeed delivering increased economy then its not coming from its octane rating or its heat value. There must be other factors at work - I don't know what they would be. It could be something as simple as Shell pumps being a little more generous with their fuel delivery - I don't know.

Maybe its the same stuff they used a couple of decades ago - 'The Mileage Ingredient' - anyone remeber those ads?
Benefits of Optimax... - Mad Maxy
Hmmm. Interesting.

I have an 03/03 Audi A4 2.0 FSI. Tried Optimax once and it seemed an expensive experiment for no discernible difference (about 550 miles on a 70-litre tankful and what felt like the same performance).

Maybe I should try a few successive tankfuls? Or just use Shell or Texaco normal unleaded with detergent additives?

Do any of you experts reckon that I shouldn't be using ordinary 95 RON fuel in that FSI (direct injection) engine?
Benefits of Optimax... - carlh
'Maybe I should try a few successive tankfuls ?'

Mad Maxy - I first used Optimax by topping up a half full tank. You probably won't see an immediate difference on the first tankful, it took me three fills but, like HJ, I have now calculated a small but definate improvement in MPG.

I travelled up the M6 from Crewe to Preston yesterday afternoon, the traffic was stop start so I just sat in the inside lane virtually all the way. I averaged about 55 mph including the off motorway bits. When I got home, the mpg average reading was 47.2mpg, aircon on all the time. Not bad for a 2.0 Golf.
Benefits of Optimax... - Roger Jones
Mad Maxy

What do the handbook and the sticker on the inside of the filler-cap cover say? You needn't go any further than that in terms of RON . . . And a few secs later, a Web search gives us "Super Plus unleaded, 98 / min. 95 RON". If that is confirmed by the handbook, it looks like 95 RON is adequate but not optimal. I would err in favour of Optimax, but then I spoil my cars.

Your 70 litre tank reminds me of the 500-mile range of the 80 litre tank in my old Audi 100 and makes me envious.
Benefits of Optimax... - Vin {P}
"it looks like 95 RON is adequate but not optimal"

Not necessarily - my understanding is that going up to higher octane fuel does not necessarily mean improvement, so adequate may equal optimal. Once your engine has stopped knocking, you can add as much octane improver as you want and you're not going to see further improvement.

Anyroadup, I've suggested today to Top Gear that this would make a good subject for an article. You never know, they might even do it.

Benefits of Optimax... - Roger Jones

Good point, but in "Super Plus unleaded, 98 / min. 95 RON", why does "98" appear before "95" and what does "min." mean if not "minimum requirement"? (Assuming that the quoted matter is consistent with the car's handbook, of course.)
Benefits of Optimax... - spinner
I've been using Optimax for a year in an Accord 1.8. It runs more quietly with this petrol.

I've had up 40mpg mixed cycle in summer, and 32mpg in winter, but that could be put down to driving style.
The throttle response is more smooth, which suits my style of driving; the power output is more even across the rev range, as opposed to lower RON petrol.

It does vary from batch to batch, though, but the effect is very obvious when another brand or RON number is used and it takes 2 fills of Optimax to get the engine back to normal.
The car is more noisy on 95/97RON, and there is more of a jump when it goes onto the second cam lobe.

It would be difficult to design a well controlled scientific experiment to prove this, and the oil companies wouldn't fund or sanction this type of study.

I think Honda make lawnmowers as well :-)
Benefits of Optimax... - clariman
My own experiment on a 1.8 litre car .........

Date Type Litres Mileage MPL MPG

02/07/2003 Unleaded 42.00 28,975 7.57 34.41
12/07/2003 Unleaded 39.00 29,270 7.56 34.38
18/07/2003 Unleaded 19.00 29,413 7.53 34.21
25/07/2003 Unleaded 19.00 29,556 7.53 34.21
06/08/2003 Unleaded 36.00 29,846 8.06 36.61
13/08/2003 Unleaded 45.00 30,185 7.53 34.24
23/08/2003 Unleaded 34.00 30,450 7.79 35.42
04/09/2003 Optimax 43.00 30,761 7.23 32.87
18/09/2003 Optimax 49.00 31,134 7.61 34.60
30/09/2003 Optimax 37.00 31,449 8.51 38.69
10/10/2003 Optimax 38.00 31,752 7.97 36.24
23/10/2003 Optimax 33.00 32,007 7.73 35.12
07/11/2003 Optimax 39.00 32,323 8.10 36.83
18/11/2003 Optimax 30.00 32,541 7.27 33.03
30/11/2003 Optimax 36.00 32,815 7.61 34.59
13/12/2003 Optimax 39.00 33,131 8.10 36.83

Not very conclusive, but Optimax looks slightly better.
Benefits of Optimax... - flatfour
I remember filling my uncles 3.5 rover V8 with 2 star instead of 5 star, had to take it back running like a pig! if optimex made this difference to my Saab 9-3 turbo no way would i use the cheapest supermarket petrol available.

I asked a mate who knows a guy that delivers for a major oil company and he says there is no mystical bottle of chemicals added to the delivery when its their own stations.
Benefits of Optimax... - Honestjohn
Unsubstantiated libellous postings have been removed from this thread. KB, if you are going to give us an inside story, then you have to supply a signed statement from your tanker driver friend, together with his name, address, NI number, etc so we have some comback should Shell complain.

Benefits of Optimax... - KB.
Did my post get lost in the sending ....or was it one of the unsubstantiated libellous postings just mentioned? If the former I'll send it again - if the latter I'll shut up and keep my thoughts to myself.
Benefits of Optimax... - Mudguts
I've said it before and I'll say it again:

Optimax is good but BP Ultimate is even better!

I found that with Optimax the engine in my 2.0 SI Mondeo ran smoother but even more so with Ultimate.

BP Ultimate also gives me a green tongue.
Benefits of Optimax... - KB.
I hear what you say,HJ, but surely the driver was relating his own views and saying that TESCO was good for him - better than Esso and Shell..... but only for him.

Can't see that being libellous - but who am I to say?

And as I met him in Devon - 230 miles away. I'm unlikelt to get those details you request.

Haven't posted here for a while......beginning to wish I hadn't bothered.
Benefits of Optimax... - GIM
What 'gums' up your engine (ie the 'bad bits' in petrol) are the heavy components 'cracked napthas'.... Shell claim: "that Optimax doesn't contain these heavy constituents". Also Optimax is 'ultra low sulpher'.... good for the planet.
I use it in my car (and I work for one of the other oil companies).
Benefits of Optimax... - Doc
Your average for unleaded is 34.782 mpg
and your average for Optimax is 35.422 mpg

This represents an increase of 1.84%

Is this worth the extra price incurred by using the Shell product?

Benefits of Optimax... - Big John
I initially noticed an improvement of around 2mpg in my Octavia 1.4 (46 mpg in the summer!)using Optimax. Trouble is when you start getting used to the extra performance the MPG then gets worse!

Benefits of Optimax... - hxj

So from the Shell website:

"Shell's experience with the introduction of this type of fuel in other countries has frequently led to a strong customer response claiming fuel consumption benefits. So while we are not claiming fuel economy improvements, there is every reason to believe that this will occur for many customers."

Optimax is all about enhancing performance, not about increasing economy. Clearly iof there was valid increase in economy then they would trumpet this from the rooftops.

Its 10% more expensive at my local Shell garage, I didn't notice any difference. I also think that there is a bit of psychology going on here. The 'placebo effect' is well known in medicine. In other words if you give patients a sugar pill and tell them that it is a wonder drug then invariably an improvement is reported. In other words you perceive what you want to perceive.

In addition many people will behave subtly differently when they know that their behaviour is being tested. Clearly there is always a risk when undertaking non-blind tests that you modify your behaviour to get the result that you feel is right. For example you drive slightly slower and accelerate slightly less rapidly without really giving it any thought.

To expalin further a test was done with children whose parents stated that tartrazine made their children hyperactive. Dirnks were given to four groups of children. A were given tartrazine containing drinks and their parents were told this, B were given tartrazine containing drinks and their parents were told that it was free of tartrazine, C & D were both given tartrazine free drinks and again one set of parents were told that the drinks were tartrazine free and one was told that the drinks contained tartrazine.

Overall by scoring activity there was no statistically significant behaviour difference between the four groups. However the groups were the parents were told that their child had been drinking a tartrazine drink reported significantly higher 'hyperactivity' amongst their little darlings than those that had not been told that they had not received any tartrazine.

In other words it is (mostly) all in the mind.
Benefits of Optimax... - El Hacko
..and in Shell's balance sheet bottom line
Benefits of Optimax... - M.M
hxj is spot on the mark.

I'm quite happy for anyone to use any fuel or device with their car and be satisfied it works for them, but if they are to offer it as *proof* for others then some proper *double blind* testing is needed. Whatever folks do they always report an improvement if that's what they were wanting.

There is a very famous experiment from the USA with factory workers where a real improvement was made to their production line.... and output went up.

They were then told a further improvement was to be made and output went up again...but in fact they'd returned the circumstances to the start position.

Then they put the improvement back in place but told the employees they were removing all enhancements...and yes true to human behaviour the output dropped right back again.

Most of the vehicles I look after run a lifetime on Tesco or Sainsbury fuel with good economy and no problems.

Benefits of Optimax... - No Do$h
Before I saw the light and got a diesel I used to fill up from time to time with Optimax. Did this every third or fourth tank purely for the extra cleaning, much like Redex but I worked on the basis that perhaps Shell may be a bit further ahead of the game on fuel detergents.

On the same basis, I add Millers Diesel Power Plus to my tank on every 3rd fill now.

Seems to keep everything tickety-boo and I notice less injector clatter and pump noise when I've added DP+, so the added lubricity is helping.

Likewise, the old Rover tended to start sounding a little rough by the end of the last tank of "regular" unleaded. Bear in mind that the Rover had the Honda engine, which was capable of running on a lower RON than than the K-series lump, so the addtional octane rating wasn't really going to make the slightest difference.
Benefits of Optimax... - Canon Fodder
and in Shell's balance sheet bottom line

Yeah, I'll second that El.

If normal unleaded sells for 75p and Optimax for 80p then as the 60p per litre [or whatever] duty is the same for both, then optimax makes 33% more revenue for Shell - Nice!

Benefits of Optimax... - Big John
I thought you paid more duty on super unleaded?
Benefits of Optimax... - patently
If you have a performance benefit then you also have a fuel economy benefit. If (for a specific fuel input) you get more power from the engine then to cruise at the same speed you can lift the pedal slightly. Result... lower fuel consumption.

So Shelll's choice to market Optimax as a performance enhancer is simply that, a marketing decision. No doubt the availability of Michael Schumacher and Ferrari to help promote it was a relevant factor.
Benefits of Optimax... - spinner
Of course there is the placebo effect,
'.. the measurable, observable, or felt improvement in health not attributable to treatment'.

As a scientist, one always has to be aware of how objective ones interpretations of experimental data are.

I haven't seen any data to prove/disprove my own views on Optimax. I personally like the stuff - because it really seems to make the engine run more quietly and the VTEC isn't as peaky. The car's happy, I'm happy.

However as a caveat I also admire Schumacher's abilities as a racing driver, so perhaps I am deluded?

Benefits of Optimax... - PR {P}
My GTA's handbook says to use petrol with "at least" 95RON. I tried a tank of BP Ultimate. I noticed a slight decrease in mpg and no noticable improvement in performance. It was only one tankful, and maybe you get an improvement in performance if constantly bouncing off the redline, but in everyday conditions for me, it doesnt justify the 6p per litre more, so I wont ever get it again.
Benefits of Optimax... - Quinny
Very interesting thread this.

I do Autograss racing in a Class 1 Mini,(Standard class) and not only do a lot of my fellow Class 1 competitors use it,but others in the more powerful classes use it as well.While I'm not saying that every competitor in every class uses Optimax,the ones that do,swear by it for better performance and more responsive throttle.

However,because a lot of engines in Autograss racing are of the leaded variety,additives are used as well,the one recommended by our governing body is Millers CVL which is an octane booster and lead replacement.I personally use Castrol Valvemaster,which is similar to CVL,and the both claim an octane gain of about 2-3 points.

I must say that my engine seems to run better when using Optimax,and while mpg is not important in our sport,anything that helps you gain the slightest advantage over your competitor is most welcome.
Benefits of Optimax... - hxj

I don't think that there is any doubt that Optimax gives you a performance advantage. Where the doubt, quite rightly, lies is whether this automatically transfers to a efficency advantage. My personal view is that any such advantage is more than outweighed by the cost.

On the other hand if you do low mileage or like it that is entirely your choice.

Performance is simply not important enough to me.
Benefits of Optimax... - El Hacko
Also a low mileager, I enjoy (and am happy to pay up for) the little extra power I get with Optimax - that's cos my vehicle is the disappointingly underpowered Lexus 200 auto.
Drove a Golf Diesel Ti today - what a superb (and economical)performer compared with the Lexus.
Benefits of Optimax... - Aprilia
Well, I just went to look at the Shell Optimax website. Not a lot of valid technical information there!. I did manage to find a calorific value for the fuel - 10790 cal/g, which converts to 45.3MJ/kg - which is typical for UK petrol - so no extra energy in Optimax to account for the suggested extra performance.

I note that they only make comparison against 95 RON fuels. They state 'up to 5% better acceleration' cf. a 95RON. They then extrapolate this to suggest up to 1.5% gain against a 'normal' super-unleaded 97RON fuel. All this assuming your car can re-map to the higher octane rating etc etc. Unfortunately it is all dressed up using words like 'up to', 'may' etc. without any solid technical data to back up these claims.

They also make the curious statement that Optimax will, "flow
more quickly & smoothly into the engine enabling earlier combustion". I fail to see how it can combust any earlier since this event is determined by the spark timing.

I am prepared to believe that Optimax has beneficial cleaning agents (detergents), but the rest of the claims seem to be salesmanship. However, its a free country and if people want to believe in Optimax and pay the extra then that's their choice.

I suspect that this argument will rumble on indefinitely unless/until Shell produce a full set of proper performace data. They could even use an independent test facility such as MIRA and use the results in their advertising (assuming they can demonstrate the claimed improvements).
Benefits of Optimax... - Cyd
I cannot help agreeing with Aprilia, based on my own experience:

I decided to give Optimax a fair trial by using it for three successive tankfulls. I made sure the tank was nearly dry before filling with Optimax for the first time and then ran the car as normal for three full tanks (around 1000 miles, 3-4 weeks motoring).

I found my overall economy on the regular commute fell from 29.5 to 27.8 - despite making a conscious effort to drive "normally". At the end of the third tank, using my own stopwatch, I could detect no measurable improvement in performance across a number of speed increments.

The only positives I could detect was that the engine did seem to run slightly quieter and pick up from a standstill was a tad better. Cold running hesitancy (sticking valves, apparently) was unchanged.

I run a Rover 820 Vitesse Sport, which ought to be able to make use of any octane improvements. I run it full time on Tesco fuel (standard unleaded). For the record - on standard tesco fuel at Alconbury airfield about 2 yr ago, with Revs timing gear onboard and me driving, the car could better the 30-70 thro' the gears acceleration time as published by Autocar when they tested this model (I got 6.5 vs Autocars 6.8 secs). This despite dodgy HT leads (changed about a month later), needing a new clutch and having crap tyres (also both changed since).

Most of my motoring is cross country flying. If Optimax could give me more mid range oomph then I'd use it more often. As it is I could detect nothing of worth except my wallet emptying faster. I will, however, use it for any more track days.

It would also be interesting to know whether Shell sell Optimax in the USA and what claims they make for it there!! Bear in mind that several fuel additive manufacturers have had to make massive payouts to disgruntled customers after failing to substantiate their claims in court.
Benefits of Optimax... - Martin Devon
Dear All,

Never mind Optimax. What is the 'best' diesel fuel for a modern common rail jobby?

Happy xmas to you lot,

Which Diesel Fuel - drbe
Well Martin

Funnily enough I find that Shell Optmax works well in my MB E class 320CDI!

I have been using it since it came on the market and I does seem to improve the mpg figures. I check them over a month using one of the trip computers.

On an unconnected matter (or is it?) there seems to be less "oil" in the fuel, the filler cap is quite hard to screw on and off.

Don drbe
Which Diesel Fuel - Martin Devon
Dear Sir,

Scuse my ignorance old chap, some apostrophe's included, but is Optimax a trade name for both petrol and diesel or am I being fick?

Regards's... happy xmas.
Which Diesel Fuel - kithmo
Optimax is petrol, Shell have just brought out a super diesel fuel but I don't think it's called optimax, correct me if I'm wrong. As regards the placebo effect, Hxj mentions, it's perfectly true. Try this one, after using Optimax for a while, tell yourself that although it gives a smoother response and maybe a slight improvement in performance, it is not as good as normal Shell unleaded for economy (mpg). Then go fill up with normal Shell unleaded and monitor your mpg. You will see that now you believe it, you will get more mpg from normal Shell unleaded. Spooky !

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