Well if you will get anal and always want 98/99.
If the manufacturer say's it can run on 97 then any old super will do.
when you get it mapped just make sure you have a good brand super i.e Esso.
The only time you 'MAY' notice the difference between SUL and 98/99 is on a dyno. any other feeling is just placeebo [s].
If the car is running full available/mapped timing advance on 97 then you will have no benefit running 98/99 as the ECU cannot give you any more timing advance.
If your ECU does not have closed loop knock control then the timing run will be the timing mapped regardless as to wheter you put 99, 97, 95 or cooking oil in it. although it will obviously run better without cooking oil in it.
My policy is, if I'm passing a Shell or Tesco 99 and it needs fuel I'll stop. Otherwise it gets whatever SUL I'm passing when the needle approaches 'E'.
I'm monitoring Knock all the time on mine and see no difference between any SUL or 98/99 brand.
If the timing were too close to the danger zone and gave the odd sparkle, I would suggest it's poorly mapped rather then an issue, due to your fuel choice.
|