Filtered Content: This photo may not be appropriate for work.

With older cars, a lot of us have no choice but to run premium fuel. Our high performance cars from the 60s have no computers and fancy electronics to automatically detect knock and retard the timing.

But most newer high-performance cars that specify premium fuel can actually run on lower-octane fuel just fine, thanks to these previously-mentioned computers. Of course, there is a trade-off in that power and fuel economy will decrease when using lower-octane fuel due to the computer retarding your timing to compensate. But, if you don't drive aggressively, chances are you won't notice the performance difference. As for the fuel mileage difference, you would need to check your mileage on a tank of each type of gas, figure out what percentage change in fuel mileage you got, and compare that to the price difference between premium and regular gas to see if you come out ahead or not. This will probably differ for everyone.

On the flipside: since it is commonly a 10 cent difference from regular to mid-grade, and another 10 cent jump to premium, the cost difference per tank is the same with $4 gas as it is with $2 gas. So let's say you have a 14 gallon tank. At 20 cents per gallon difference, it costs you $2.80 a tank more to fill with premium than with regular. And that doesn't change, whether gas is $2 per gallon or $4. In fact, percentage-wise, the price of premium is actually less of a "premium" over regular gas now then it was a year ago (10% for $2 gas, 5% for $4 gas.) On the other hand, even a savings of $2.80 per tankful will save you money over time... assuming your fuel mileage doesn't decrease by more than 5%... which, if you get 20 mpg city on premium, and you get 19 mpg city using regular gas, the price difference is a wash.

So, you really need to do some calculations to see if you will save money by dropping down to regular gas in your car. Of course, keep in mind, if you car does not specify premium gas, it is ALWAYS a waste of money to put premium in your tank in the first place.

So tell us: are you still using premium in your car or has your car gone on an octane diet? Let us know in the comments!