[78 GHOST]

Octane is a term describing the particular fuel's resistance to detonation.

If your car isn't running well on 87, it's because you're suffering inaudible detonation, and the car is struggling to accellerate despite this tremendous problem. Upping the octane removes this detonation, permitting the engine to achieve it's healthy level of power given the fuels available.

Octane is only helpful to the point where you're no longer experiencing detonation at the optimum timing setting. If you're NOT experiencing any detonation, your octane is sufficient and you will see ZERO benefit switching to a higher octane. In other words, higher octane fuels DO NOT contain more BTU's of energy than lower octane fuels, as is commonly perceived by the public.

However, if you build up a high C.R. engine that develops a lot of dynamic compression, you may have to set the ignition timing way retarded to prevent detonation.. thus robbing you of huge power. In addition, retarded timing makes more heat than properly set advanced timing, resulting in overheating problems.. etc.

If you build an engine with iron heads and 9.5:1 C.R., todays pump premium should be adequate to permit you to run the ideal timing without detonation. Aluminum heads require about 10.5:1 for peak pump gas power, due to aluminum shedding heat better than iron.

Ideally, you would design your setup predicated upon the fuels available, and work backward from there to setup your C.R., cam, etc.

Lead was a popular additive since the late 30's to raise the octane of a given fuel. This push was driven by the need to develop more speed from the early "pursuit" aircraft in the Army Air Corps.

Today, we use different more environmentally friendly additives to achieve the same thing.