Mixture Control

[Chuck Notyeager]

Originally Posted by Chuck Notyeager

My suggestion is visit Pelican's Perch https://www.avweb.com/news/pelican/182146-1.html Articles 8, 18 and 19 are compulsory followed by 15 and 16 and any/all the rest John Deakin has written.

You will find the answers you seek in the link to the list of articles by John Deakin, supplied above. Your C90 would have 7.8:1 compression ratio if the original pistons are fitted and if C85 pistons were fitted then this would push the compression ratio up to 8.2:1. Whatever the case, you cannot damage the engine by leaning even with forecourt fuel as the octane rating is higher than the minimum required. (Check the engine data plate for the minimum octane required.)

Please study Deakin's article No 8; "Go Ahead Abuse Your Engine." Your engine will burn cleaner, be healthier and not be damaged as some scaremongers might say.