What fuel should I be using?

[Aerotop Dave]

This is another area that can cause confusion. If you’ve got a UK car you can use whatever you want – unleaded, premium unleaded, Optimax… anything, although you’d be better sticking to premium unleaded as a minimum. If you’ve got a J Spec however you may want to be a bit more careful about what you put in. In Japan cars use 100RON fuel, and that’s not freely available over here. The nearest you’ll get is 98 RON Shell Optimax, and this should ideally be your fuel of choice. But you will have noticed that Optimax is more expensive that the normal stuff, and obviously you may live or be travelling miles from the nearest Shell garage. BP Ultimate is another high grade fuel which isn’t too dissimilar from Optimax, but after that you’re into the premium unleaded fuels which are all 97 RON. These are generally okay to use, but you’re on the limits of predetonation and the engine running a little rough. It’s very much dependant on the car itself – some J Specs run absolutely fine (I can’t notice any difference between Optimax and premium unleaded in my J Spec TT) whereas other people report noticeably rough running. Certainly once you start modifying to big power levels you’ll want to be running Optimax or similar all the time. After these fuels there’s 95 RON unleaded and this you most definitely want to avoid. If you find yourself in the middle of nowhere with just enough to buy half a tank of normal unleaded then the car will drive just fine and get you home (it’s not gonna conk out or blow up or anything) but you may want to stay off the 2nd turbo a bit to avoid problems.

 

98 and 99 RON fuel is becoming more widely available from different manufacturers - Tesco have just started a pilot scheme using 99 RON fuel, and recently I found myself in the middle of the Essex countryside filling up at a tiny 'Q8' branded station with 98 RON Super Unleaded.

 

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