Weird - my WRX used to ping itself to pieces on BP super unleaded but the problem was less on optimax:confused:

I saw an article in a magazine, I think it was EVO. and it aimed to find out the truth about Optimax. They showed pictures of valves being significantly cleaner and fuel efficiency up on a range of normal and sports cars after using Optimax.

I am a believer and it would take some REAL facts to put me off it. I have used it for a year now without fail.

my 2p's worth. We cannot buy Optimax here in Switzerland only SUL (98 ron). Went to Germany over Easter and there they have Optimax. Car (STi7) definately felt more responsive on Optimax and returned better fuel economy.

I own abig turbo escort cossie and i use SUL and Optimax and i don't notice any difference when i use either i use optimax when a can but my local shell is 12 miles away and my bp is just round the corner also optimax is about 81.9p a ltr and SUL is about 83.9p so optimax is slightly cheeper, i tend to use optimax more it has to be said

my car runs better on optimax than normal sul so I am sticking with it

[Edited by chrisp - 5/11/2003 4:04:58 PM]

Just to add to Mycrofts explanation, increased octane does allow advanced ignition and (assuming flame speed remains the same) increased thermal efficiency and therefore power. I would agree, however, that calorific value is an issue but all the SUL's (optimax included) have a very similar value.

J

[Edited by John STI 8 - 5/11/2003 6:47:07 PM]