Thu Nov 03, 2005 2:53 pm

Well, I still havent begun my gas experiment, however. With several month old regular 87 ctane pump gas in the tank, and not having run in about a month and a half, the cub fired right up with no problem at all. I will still do my experiment though, but that was good news for the pump gas camp!

Gasoline re re re revisited

Sat Nov 26, 2005 11:43 am

Carl,

You said it all!
The Cubs compression ratio I think I read somewhere is something like 6:1. The higher compression the more heat built up in the combustion chamber. When you have a high compression engine and try running low octane fuel, the heat from the compression prematurely ignites the fuel causing "preignition". A low compression engine can run on high octane fuel but not as efficently as it would with the recommended octane. High octane fuel could also make a low compression engine start hard.

Brian