Turbohot

Tell me,please!If you have been filling SUL and switch on to Optimax,do any probs occer?What if you fill any of them at different times in the car,any probs?

greasemonkey

Optimax *is* a type of SUL - it conforms to the British Standard that defines Super Unleaded fuel. The difference is that it's got some extra bits and pieces in it that raise the octane rating slightly (good thing) and also, so Shell claims, lead to a smoother running engine and better economy.

Because it's a proprietary, Shell only thing, the Optimax you buy from the garage nearest to you should be the same stuff as you'd get if you were filling up on the other side of the country, which means that no matter where you fill, with Optimax you should know what you're putting in your tank.

SUL from other refiners can theoretically vary more in its exact composition, due to the fact that the BS is quite generic, and so fuel refined at different sites, and by different companies will deviate from the standard in different ways. It lacks the detergents and other additives that Shell claim make Optimax so special, and it's also more likely that you'll get an occasional "bad" tank of fuel. In that event though, a Knocklink will give you valuable advance warning.

As for which is better, to be honest you'd be hard pushed to tell the difference between SUL from most of the major refiners and Optimax. Both are better than 95 RON Premium Unleaded, but neither comes anywhere near the rocket fuel that JDM cars run on at home.

The only thing I know is that my Knocklink is happier on Sainsburys SUL than it is on Optimax, so it's the Sainsburys brew I use