I have filled mine up with 95 once, when I could get 98 and it idled rougher and spits and farts about a very low RPM. It doesn't make a lot of difference once up and running. I image the knock sensors just retard the timing back a little to compensate.
As per Jimpom really, if you need to save £4 per fill. You need to change your car for something else.
Last edited by creepy coupe; 06-12-2012 at 04:10 AM.