highest compression you can run on pump gas?

[mx Eli]

I was just wondering what is the highest compression you can run on 93 octane no ethonal pump gas. and if a octane booster like the new lucas oil octane booster or similar product actually would work?

I have a buddy who I know runs 93 in his crf hybrid with a 13.5:1 but I wanted to know what you guys think


Thanks for your help

[motomxman450]

13.5 to 1 is very high for pump gas if your going that high I would run 50/50 race gas pump gas minimum. If not straight c12 . The hightest I would go would be about 12 to 1 maybe 12.5

[JOHNDOE83]

You will deffinetly need race gas, I would not run pump, it will ping itself to death.

[300ex mxracer]

The maximum compression for pump gas from what i've found is about 11:1 for air cooled and 12.5:1 for liquid cooled.

[Toadz400]

There's no straight answer for what is the highest you can run on pump gas. There are many factors that determine the highest compression you can run without predetonation but the general rule of thumb like 300ex mxracer mentioned is 11.5 for air cooled and 12.5 for liquid.

I have heard of a few people running 13.5 and getting away with it.