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Filled up once with normal Shell fuel (in the very far north of Scotland) after always using Optimax in my old 30v A4 Quattro. Got a real shock, the car ran so bad for 50-60 miles i dug out the RAC card from the glove box ready for the car to die! It took a couple of tanks of Optimax to come right again.

I Never use anything else in the Bora R32.

Petrol brand and type appear to make no difference at all in the wifes Saab though.

Found a website once detailing petroleum development for aircraft before the jet engine, some of the fuels used were not "petrol" (iso-octane & n-heptane) as we know it at all(synthetic chemicals & tuelene or somthing), it's comlicated stuff! Also knew a few guys who paid big money for "Bluegas" (race fuel) for their racing bikes, it gave very large power gains and the exhaust fumes made your eyes sting.

The fuel you use can make a huge difference to performace, wether the fuel you can buy does, is harder to say.
 

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Well obviously the Octane rating IS going to make a difference to the running of your car, how much of a difference i would say depends on the level of tune. A standard car that isnt regularly serviced isnt going to notice much difference in performance going from 97/98 RON fuel to standard 95 (regardless of source).

However, a standard car kept in optimal tune (plug gap spot on, air/fuel ratio as near to stoichiometric conditions as poss etc etc) would probably notice a difference, it HAS to, they ARE different fuels...

Those of us with chipped/tuned engines are going to notice a difference even more because a remap/chip is designed to optimise every setting and extract as much power/performance as possible for a given engine spec, therefore if your car falls out of tune slightly (I.E running 95 RON over 97/98), you will notice it...

Also, to re-inforce this argument, think about why chip tuning companies offer different maps for different Octane levels, this is because they can run more boost and advanced ignition timings without fear of pre-ignition or detonation for higher Octane levels.

Most supermarkets buy their fuel from the 'spot' market, which basically means from anywhere at the cheapest price regardless of quality. I remember reading (and i dont know how accurate this is) that spot market fuel 'CAN' (not always) come from a major brand refinery but without the additives, because (and this is the bit im not sure of) the spot market tanker drivers dont want to wait in line to top up with additives (the additives are added just prior to delivery apparently).

Whatever the case may be, supermarket fuel tanks must be filled with a mish mash of fuel from anywhere and everywhere...not good.
 

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Some other interesting info to throw into the debate:

[*]You read the EXACT same discussions on forums with Ferrari and Porsche owners. Hmmm.

[*]Shell have an Optimax Discussion Forum. Nobody from Shell is ever there most of the time. Whenever asked to comment, the few who do show up will not make ANY solid claims as to what Optimax actually does.

[*]Use Google and search for any hard evidence - a single scientific test - discussing the merits of Ultimate / Optimax. Let me know if you find any, because the best I could find was for Shell V Max. How can I argue with hard data like this?

Posted Image
Posted Image


This graph clearly illustrates new Shell V-Power?s superior performance advantage over the ordinary unleaded fuels on the market.

Oh but of course, I was such a moron to question its merits.

[*]Marketing. Its very easy to convince car enthusiasts they do not know what they are talking about if they use anything else. Shells website even says it:

If you care about your car, then Shell Optimax? is the fuel for you.

Well I guess I hate my car then - sorry for thinking some form of 'proof' is a reasonable thing to expect...Ill base my judgement on forum heresay instead. If you drive a chipped / mapped car thats been set up to take advantage of higher end fuels, then I can only assume it should be used. But if you drive a stock car I would spend my money elswhere personally.

PS Nectar point people, use BP - decent 95 fuel and you get points there too [:)]
 

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i also believe fuel manufacturers adjust the fuel seasonly to account for better cold starting in winter.i'd like to know how long it takes for fuel to degrade as i remmember my old two stroke enduro's ran way better on fresh fuel as opposed to what was left in from the week before.
 

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I used to work for esso and it is true that the supermarkets buy their fuel on the spot market i.e. the cheapest place at that time and this could mean that when you fill up at asda you could be getting esso,shell,bp or imported crap.It's pot luck.

I run my car on either optimax or esso supreme and can def notice the car running better.

Ever left the fuel in your lawnmower over winter-notice that it wont start until u fill it with fresh fuel-thats what fuel degredation gan do.
 
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