I guess 98 would do just fine for most builds, around here that is race fuel grade

 

thats why when i do my 440 kit its staying at 11:1, come on 12 bucks a gallon, wowzers.

v581

 

yea, when i upgrade the piston im going to get an 11:1, it takes premium, which i run anyway.

 

I run a Ross 10.75 to 1 and I run better on 87 and 89 than I do on 91

 

wow. Do you think a stock compression raptor would run better on 87 then 93???

 

When the Raptor was stock, I ran premium.

When I was a 686, 11:1...I ran premium.

Now that I'm running a 14:1 Ross, I am running straight C16 VP race gas.

With a 12:1 I would run atleast 100octane or above.

 

You need to run the fuel that will bring you just past the point of detination...Try an 87 and then try an 89...Dyno tests have shown that by reducing the octane level the higher the h.p. Low octane fuel has a higher flash point than high octane fuel....The more compression you have, the less flash point you want because the compression is so high that it hardly takes much to ignite the cyliner....The lower the compression, the higher the flashpoint neccesary to ignite the cylinder[img]i/expressions/face-icon-small-confused.gif[/img]

 

What about premium 92 (i think) mixed 50/50, thats about 95 running 12:5-1 compression on YFZ.

 

ItalianStallion has the best answer so far, I'll just add altitude has alot to do with what you run, and race gas does burn slower and helps keep the heat down on high comp engines, but the lower the octane you can run the better. You dont use race gas to get power, you use race gas because you have so much power you need to protect the engine, help it run cool and stop pinging and all that.