Octane question about M42/M52
This is where I get confused about these engines.
I always ran my M42 on 91+. Some owners keep saying that M52 328is run on midgrade (89octane)..
How is it that M42 that came in 1991 uses 91octane fuel ? Than you got M52 1996 + that uses 89octane? I used to think that more powerful M52 would run 91+.... How is this the case?