Posted: Apr 06 2006 at 10:44pm | IP Logged

This topic has been argued many times before...see the excerpt below or use the link to read the entire article.

http://www.straightdope.com/columns/041008.html

.....Contrary to widespread belief, the octane rating doesn't indicate how much power the fuel delivers; all grades of gasoline contain roughly the same amount of heat energy......The majority of cars are designed to run on regular gas, and that's what the manuals tell the owners to use. Higher-performance cars often require midgrade or premium gas because their engines are designed for higher compression (higher compression = more power), and regular gas may cause knock. If your car needs high-octane gas, the manual will say so.....Using high-octane gas in a car designed for regular accomplishes little except more rapid combustion of your money......Believe what you like; the point is, don't assume "premium" means "better.".......