Over the years I've heard people who own a high performance car say "oh, I know it's supposed to take premium, but I use the cheap stuff anyway." I drive a Honda Prelude, and the 5th generation models are designed to use premium gas, as are a number of other high performance cars (i.e. foreign sport compacts, domestic muscle). The reason for this is too much to be explained here, but long story short I can tell you that it does not hurt the car in the short run to use regular. Modern automotive computer systems will detect lower octane rated gas and adjust the engine's timing to compensate, BUT the result is decreased performance. If you drive a high performance car, performance was probably one of the biggest reasons you got it (unless you are female and just like the color). Anyway, using inferior gas on a car that was designed for the good stuff is just plain stupid and I can prove it:
1. If you are worried about saving money on gas, why did you buy a high performance car in the first place? If the answer is "I don't know" or "I just like the way it looks" - you should make friends with people who get their combo meals at McDonald's with a Diet Coke. That way neither of you will feel burdened by each other's lack of intelligence.
2. The difference between regular and premium in most places is $0.20/gal. Yes, that's one-fifth of one dollar. To illustrate what that really means, let's say you have a 18 gallon tank, which is quite large for most 2 door cars. When your gauge is at the empty mark, you would probably have about 2 gallons left in reserve, which means to fill up you would have to buy 16 gallons. Buying premium would mean spending 16 * .2 = $3.20 extra per tank. If you fill up once a week, that's 3.2 * 4 = $12.80 per month. Honestly, is twelve dollars and eighty cents REALLY going to break the bank? If so, you should have bought a different car to begin with.