As with all things in life buy the best you can afford. I am sure that the use of 95 or even 97 RON can't do any harm short term but the manufacturer does say 98 RON and they do this for a reason. The engine is very high performance for a normally aspirated road car and it deserves the best fuel you can stick in it.

When i've had to use 95 RON I've always bought a good brand and limited the revs until I can fill up with the proper stuff again.

 

When I picked my S2000 up from the dealer I asked what fuel they recommended and was told to use 95, which I have been using ever since. I can't remember the reason given, but it went something along the lines of there is no performance advantage using anything better with this car so it's a waste of money.
I took it as gospel but am now beginning to have doubts.

 

Dealers are, by and large, staffed by idiots, momo.

Look inside the fuel filler cap.....

 

Right, time for a few facts

Your car has a knock sensor which is what allows your car to take advantage of better fuels, or help protect it if you put crap stuff in there.

Using 95 fuel WILL NOT harm your engine in any way. Your ECU will just retard the timing to an appropriate level and you *may* knotice it being a touch less responsive and a touch less poke.

Now, if you use Optimax or another 99 fuel, your ECU will take advantage of it. Optimax is designed to give best performance, Bp ultimate is designed as an SUL and its selling point is its cleaning potential and increased MPG. A lot of people make the mistake of comparing them on a performance basis.

Supermaket fuels... They all come from the same main depots in the UK, and it is true that the various tankers from Shell / Tesco / Sainsbury etc will then pull up and add in their own additives. Additives cost money, and supermarket ones do skimp here. They do admit to selling fuel just being a "serivce" and help pull people in for shopping. the additives can range from stuff that eats carbon, to inhibitors etc... I have never bought supermaket fuel. (I do work for an oil company though )

At the end of the day, on the S I wouldn't get too excited about it. Try and use a good SUL and stcik to it. The bonus of Optimax comes in when mapping turbo cars, the difference between it and other stuff then becomes pretty clear.

Please please nobody post up saying I stuck in some optimax and the car really flew For one the ECU does take time to adjust to a better fuel (quick to react to a poor fuel & therefore knock though), sometimes a fair bit of a tank. Secondly, its a few bhp we are talking here and you lose more by putting the air con on

MB

 

I'll try and use BP Ultimate every few tank fills for the cleaning stuff. Not too bothered about which other SUL I use. Usually it's Shell or Total, as they are the most convenient petrol stations for me.
There are too many other variables such as the weather which affect the performance of the car to say which petrol performs better in the real world imho.

 

Yup, totally agree Pip. I use the odd tank of ultimate for the same reasons.

MB