by John H » Tue Jan 24, 2006 9:30 pm
Just use whatever octane number or RON is in your user manual.
If you use a higher octane fuel than the engine is designed for, you're not going to get any more power despite paying more per litre for the fuel, and in some cases you'll actually soot up your spark plugs because of the slower flame front of higher octane fuels. Higher octane does not mean higher power unless the engine it's running in is designed to take advantage of the combustion characteristics of higher octane fuel.
If you use a lower octane fuel than the engine is designed for, you'll potentially end up with the engine pinging. The reason a lot of modern fuel injected engines (eg European car engines) will develop more power with higher octane fuel is because they're designed for higher octane fuel, but can also detect lower octane fuel and adjust the ignition accordingly to prevent knocking (although power is reduced in doing so).
Of course BP Ultimate might be a better choice than standard octane ULP from a dodgy operator who adds ethanol, paint thinner, and any number of other things to it. But providing the fuel is of equivalent quality, there is no performance advantage in running any other fuel than the one the engine was designed for in the first place.
At least that's what I've been told.
'01 Kawasaki ZZR250 (my motorbike)
'96 Daihatsu Charade TE (my other motorbike)
'91 Alfa 164 3.0 V6 (a.k.a. the money pit)