Ratio Explanation

[mrelmo]

Never really had an explanation for the 50:1. I assume it is 50 parts gas to 1 part oil, but when people say leaner or richer I'm not sure which way the mixture goes. Would 60:1 be richer or leaner?

 

[Droid]

The higher the number, the less oil. 50:1 was pretty much the standard from the early 60s and later for engines requiring pre-mix.
Oil systems like OMC VRO (variable ratio oiling) did just what the name implies, leaner at idle.

 

[mrelmo]

thank you

 

[makomark]

FWIW richer or leaner, in the context of in internal combustion engine, usually refers to the air-fuel ratio...

 

[mrelmo]

Right that is how I always looked at it