The lowest octane your car will run it's best on. Lower octane gas burnes better and more completely than higher octane gas. There's no "one" answer for every car but many make the assumption that higher octane gas is better. If your car will run through it's power band on 87 octane octane gas without pinging then that's your grade of gas. If your timing is advanced, then reducing it to near stock in order run a lower octane gas for the purposes of emissions will be your best bet for reduced emissions.
The lowest octane your car will run it's best on. Lower octane gas burnes better and more completely than higher octane gas. There's no "one" answer for every car but many make the assumption that higher octane gas is better. If your car will run through it's power band on 87 octane octane gas without pinging then that's your grade of gas. If your timing is advanced, then reducing it to near stock in order run a lower octane gas for the purposes of emissions will be your best bet for reduced emissions.
My timing is at 14 degrees. I've run 87 octane on that with no problems. Should I run it though with 87 octane with advanced timing, or reduce the timing also?
if you're running 14* on 87 octane now then I'd suggest you let it be. It sounds to me like your internals are all very clean and you shouldn't have any trouble passing emissions so long as the rest of your emissions equip is up to par and your compression is good. With 14* timing and 87 octane gas with no detonation problems, I'd say that you're probably burning pretty clean.
if you're running 14* on 87 octane now then I'd suggest you let it be. It sounds to me like your internals are all very clean and you shouldn't have any trouble passing emissions so long as the rest of your emissions equip is up to par and your compression is good. With 14* timing and 87 octane gas with no detonation problems, I'd say that you're probably burning pretty clean.