Original Message

Agreeing with, and picking up on what StockcarRacer2X says above, what is the advantage to running racing fuel if running a class of car where the engine won't "appreciate" it?

I don't know that much about fuel, but I know a little about octane and was always taught that the octane ratiing is basically an indicator of how "patient" the fuel will be, and the higher the octane #, the more it would wait for exactly the right time to light off (would wait for the spark to arrive to light things off exactly when you wanted it too.)

This is why if any of us had a passenger car back in the 70's that would ping on 87 octane, the easy work around was to run higher octane 89 fuel.  You weren't really fixing anything, but the ping was gone because the higher octane caused the light off time inside the cylinders to wait just a little longer (hopefully until the spark arrived) so that you were no longer having pre-ignition due to higher than expected temps in the cylinders.  Stuff like red hot carbon spots on the back of the valves.... over advanced timing... too lean of an air fuel ratio... or in some cases, a disconnected or non functioning exhaust gas recirulation (EGR) valve.

What might surprise a lot of folks is the lower the octane #, the easier it is to "blow up"/ignite.  That means that 87 octane is easier to light off than 89.. or 93... or 103....  I was taught that it's not that higher octane makes more power, its that the higher octane allows for more squeeze (higher compression ratio), or allow for boost via a supercharger or a turbocharger... or allows for a more agressive "tune."  So, in those scenerios (high compression engine, boost conditions, agressive timing curve) the higher octane allows for more potential power, provided all the other pieces are in place, and somebody was smart enough to then tune to maximize that potential that the higher octane could not be counted on to "wait" for.

Does anyone know what the compression ratios are of the different "crate" engines that are likely to be running at the local Saturday night track?  I don't, but for those considering what fuel makes the most sense factually (not emotionally, not "well that's what I heard from so and so...." they might want to find out the compression ratio they are running and even more specfically what the engine manufacture's recommendation is to get the most out of that "crate" engine.

Otherwise, I question would there really be a difference?