Ducati Sporting Club UK > Model Specific - Discussion, Technical Problems and Help > General Motorcycles only > Shell Optimax

[gaz3014]

Ive got an Jap spec Subaru sti9, and it had to be re-mapped, cos it was mapped to run on 100ron fuel, which is what they have in Japan!!!

I was warned not use anything apart from optimax, for risk of detonation if driven hard. If I had no choice due to lack of a shell garage, then I could use a lower grade, but keep it below5000rpm.

I have been putting it in my 999R, and it has definatly made it smoother, as she was a bit sluggish untill she got going!!

Just my 2 pennies worth guys!!

[baylissboy]

I've always used optimax or BP ultimate in all my cars & bikes!! Unleaded is for lawn mowers only!!

[749er]

Originally posted by Ains.


In short and in general the higher the compression ratio the higher the octane needed, although modern engine management has minimised knock and pinking so a higher CR can be used for the same grade of petrol than of old.

I also think I am right in saying our low grade fuel is actually higher than in the USofA; 87 for the US. Wos ours 90 something?

Ains.

In the US their fuel is rated as MON not RON hence the different values between UK and US fuel ratings.

I am not aware of Ducatis having knock sensors, modern cars do, especially turbo cars. These monitor for detonation which would otherwise destroy an engine. Running lots of boost on a turbo can lead to det, but using a higher octane fuel can allow a cars ignition to be advanced. 1 degree advance can provide up to an extra 10bhp, which is where the above mentioned scooby prolly got its power. It had to have some kind of fuel/ignition controller as made by Greddy or Apexi to get that kind of gain. Similarly WRC teams would run water injection systems to allow the timing to be advanced. Water cools the cylinder reducing the risk of det. The oxygen released also aids combustion, particularly if the water is mixed with ethanol, which of course gives a bit more fuel. In comparison to what can be done to a car, PC111s are very very crude.

I run Optimax and most definitely feel the bike pulling stronger