Quote:
Originally Posted by djm96z28
I've been doing that on my '96 Z28 since it was new - never had a problem. I filled up with Premium (93), then at 1/2 tank fill up with mid grade (89). That averages out to 91 octane--which is considered premium grade. Helps save a little money gas-wise.
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Octane rating is the amount of lubrication in the gas. The higher the octane rating the more lubiraction in the cumbustion chamber via the gasoline so the car can be tuned for more advanced from TDC, thus allowing the engine to run harder. the reason high compresion engines need higher octane is for the closer tolerance between parts. An old trick in making an engine run better at higher rpm was to advance the timing on an engine but the draw back was engine knocking and a hard engine to start so the trick was to adbance the timing enough to get good high rpm performance but still be able to start the car and avoid knocking when you turn the car off or at idling. The higher octane allowed us to advance the timing and not get knocking when the car was turned off. Now these days, the timing advancement is managed by the on board computer but the programming is dependant on the higher octane to protect the engine parts from knocking into each other.