A VERY basic primer on octane rating can be
found here.
For those with too little time to read it, the important parts are:
Severe knock causes severe engine damage, such as broken connecting rods, melted pistons, melted or broken valves and other components
(this is known as bad things). The octane rating is a measure of how likely a gasoline or liquid petroleum fuel is to self ignite. The higher the number, the less likely an engine is to pre-ignite and suffer damage.
Many high-performance engines
(GSR's) are designed to operate with a high maximum compression, and thus demand fuels of higher octane.
A common misconception is that power output or fuel efficiency can be improved by burning fuel of higher octane than that specified by the engine manufacturer (premium in a non vtec engine). The power output of an engine depends in part on the energy density of the fuel being burnt. Fuels of different octane ratings may have similar densities, but because switching to a higher octane fuel does not add more hydrocarbon content or oxygen, the engine cannot develop more power.
However, burning fuel with a lower octane rating than that for which the engine is designed
often results in a reduction of power output and efficiency. Many modern engines are equipped with a knock sensor (a small piezoelectric microphone), which sends a signal to the engine control unit, which in turn retards the ignition timing when detonation is detected. Retarding the ignition timing reduces the tendency of the fuel-air mixture to detonate, but also reduces power output and fuel efficiency.
(If your engine does not have a knock sensor or it is disabled or non functioning due to modifications refer to the paragraph on bad things.)
Synopsis: If you do not have an Integra with a vtec engine you should run regular gasoline and save a few pennies at the pump. If you have a GSR (vtec) you should run premium and pay the few extra pennies and not b**** about it.
Sorry, this is a long winded way to repeat what many of you have said earlier.