I work at a servo and there is an interesting fact that you should all know. Mobil Synergy and BP ultimate is the same fuel. It is made by Mobil and sold to BP. So all those gains to be had from switching between the two...?? Optimax seems to be about the same, however it goes off much quicker. Not usually a problem, but something to note. Caltex is utter crap, especially in a performance/hi compression engine. In addition to all this, you have to remember that to be accurate with your comparisons, the fuels cant be mixed and must be flushed between change-of-brand fill ups.