What Octane to use

[Guest Warren Rhen]

Reading my shop manual it says to use 97 or 95 RON(I think. I don't have the manual here now) What does that translate to here in the USA in comparison to what is listed on the pumps. I'm not experiencing any pinging with 91 but I thought that with only 9.3 compression ratio I should be able to use 89 or even 87 in cooler weather. Also I read in an older post about occasional spitting and couphing problems as well as stalling occasionally at red lights but I didn't see any cause or cure for the problem. Anybody know? BTW my LeMans has a PCIII and Mistrals

[Frank]

Warren,

 

Octane ratings are obtained by two methods, Research and Motor. That yellow sticker on the pumps that says R + M/2 is an average of the two methods. If I remember correctly, the Motor octane is a more severe test and typically, the number is about10 points less than the Research number. When all this started many years ago, I just remembered add about 5 points to the R+M/2 number to get an approximation of the old octane number(which I believe was the research number).

 

Frank