I mix 5 gallons of 100 Racing fuel and the rest with premum

 

Race gas or high octane gas does nothing for you unless you have the compression to warrant it. Back in the old days gas had lead which increased octane and helped lube the valve seats, if your heads have been rebuilt in the past 20 years you don't need lead. Octane is a measure of a fuels ability to resist pre-ignition (pinging) if your car does not ping on 89, you won't get any more power from 93. You can RETARD timing to help eliminate ping, not advance. There is no reason to run race gas on anything with less than 11.0 compression, it's just a waist of money.

 

I run super. Since I get about 4 months to a tank of gas, don't mind spending the little extra.

 

+10,000

Also, don't the new LS7's have like 11.0:1 static? They run just fine on premium pump gas, though I imagine better fuel and a tune would pick up a fair bit of power. I'm assuming they run a conservative tune out of the factory

 

I run 89 in my 9.3:1 331 with 14* initial advance and 32* total., works great.

Octane is an additive to stabilize gas during combustion. It actually makes it harder to ignite, and slower to burn. If you run gas that doesn't have enough octane, the gas will preignite on hot spots in the combustion chamber, or it will detonate instead of burn.

However, if you rungas withtoo high of an octane in your car, it won't completely burn, which drops efficiency and leaves deposits in your chambers.

If you've got an aggressive cam with a lot of valve overlap, you can sometimes get away with using lower octane gas. The valve overlap means you don't produce as much dynamic compression at lower rpm's, so even if you load the engine up at low rpm's (textbook case for detonation with low-octane gas), you don't have enough pressure tocause detonation. This is how I get to run 89 in my 331

 

Wow, here in Australia our standard fuel is 91, premium is 95 and top of the range is 98. I use the 98 all the time. You pay for it, but can run higher compressions and timing. (maybe we measure the octain rating differently here?)

 

Well here in california it goes 87, 89, 91 octane and i've put 91 only in my mustang just because I love her but it probably needs it, has a newly rebuilt 351w, not sure on compression. There are some shell stations around here that sell 100 octane race gas, but I havn't tried it. Once day I might mix a few gallons in that with the 91 to get like 94 or something.

 

If it doesn't ping on 91, don't use anything more. If anything, you might try putting a couple gallons of 89 in next time you empty your tank, see if it works. If you get pinging under light acceleration while going up a steep hill, go back to 91. If not, stock with 89.