Excuse me for being a little blond, but isn't the needed octane number related to the compression rate? That is, if an engine has a very high compression rate, it might need 98 or even 100 octane, if not 95 is enough. No modern engine I know of in road going cars has anything that really needs 98. Of course you can put it in, but you will achieve no benefit. I had an old Sierra that was specified for 98, if you put anything lower in it you could risk premature firing just by the compression (like a diesel), not the spark from the spark plug. But not so with a modern car. I also had an Elise - tried with both 98 and 95, noticed absolutely no difference. I hardly think that the MW3 S&S engine is high compression and really needs 98. So, if the engine can tolerate 95 anything above is a waste money, if 98 really is needed anything below can/will cause problems. Or am I totally wrong?
