Newer pcm's can run fine on 87 octane. They have "low octane" spark tables. They will NOT detonate from JUST running 87 octane, it's when you combine that with a lot of heat that you'll start to ping.
There is no more energy in 94 octane than in 87, it's virtually the same amount of btu's. What does this mean? Well it means you won't loose any gas mileage by going to a lower octane (so long as it's not running noticably different). With that being said, it's why I run 87-89 in any sbc with fastburn style combustion chambers and less than 10:1 compression. Add a larger cam and the dynamic compression changes, this in reality lets you run LOWER octane than a tighter cam! The only trouble with this is at WOT where you might be building up a lot more heat in the combustion chamber at high RPM... this is why specific output (horsepower/displacement) is proportional to recommended octane. You can, and I've done it, run a 14.6:1 compression tight cam race engine (600cc motorcycle) on 93 octane. It'll run fine up until about 8000rpm
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Take it from me, you guys can run 87 octane without ANY problems. Just don't ring out the engine and if you want to have some fun fill up half the tank with premium and go at it. 89-90 octane is fine for a <400hp Lt1/vortec sbc. LS1's are even more resilient.
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, Jon
Owner of a Red Sled.
If it\'s EFI I can tune it. Specialize in 82-95 GM (yes Lt1\'s)
\"If you can leave black marks on a straight from the time you exit a corner till the time you brake for the next turn.......Then, you have enough horsepower\" - Mark Donohue
