Fuelish

My son, the car aficionado, is the only person I know personally who has purchased premium gasoline. On purpose. It is entirely possible that once upon a time when I was dong my due diligence and pumping my own gas that I may have inadvertently pushed the wrong fuel grade button. This is one of those odd indicators to me, by the way, that all this worry about supreme and hi-test and so forth may be a lot of hooey. There was a time when there were actually separate pumps for the special fuel that would not have been an issue. Pull around to the regular pump. I don't need any of that fancy stuff for my car. Besides, it was the late, great Mad Magazine that provided me with the image of a single tank buried beneath a series of gas pumps all labeled with various exciting names and qualities. It's all gas, right?
Well, certain auto manufactures recommend that you use premium gasoline in their very fussy engines. Luxury types. And that's "recommend," by the way. It's a way to to ensure that you keep feeling luxurious even when you're standing there at the self-sever island wiping your own windows while your tank fills.
What makes gas supreme? It's the octane rating, usually a matter of four or five points. Regular, run of the mill, garden variety gasoline sits somewhere around eighty-seven, and that liquid gold you yearn to pump into your fancy schmancy performance automobile comes in around ninety-two. Since that translates to around twenty cents per gallon and you're driving that schmancy car and affording the payments then you probably don't mind spending an extra two or three bucks per tankful. 
And yes, lower octane gasoline is a little more likely to cause engine knock, caused by a preignition in your car's cylinders that doesn't count as a full ignition. This means your engine isn't properly compressing, which might not be so bad coming from a Dodge Dart, but a Bugati Veyron is another matter. Your Dodge Dart has a low compression rate, so you probably won't notice it. That Bugati, on the other hand, has a very high rate of compression and you had better keep fancy gasoline in that bad boy or there will be trouble. Not a lot, mind you, since Modern engines use a device called a knock sensor to detect the rattling and vibration within a cylinder that signals preignition. These sensors send a signal to the vehicle's Engine Control Unit which then adjusts the engine's timing when the spark plugs fire to reduce or prevent the knock. You might not win that street race against Vin Diesel, but it's pretty tough to notice on a trip to CVS. 
And if you're worried that regular gas won't keep your engine clean like premium will, remember that Environmental Protection Agency regulations require that all grades of gas have detergent in them. So, if you're driving that Bugati and you can afford it, hire me to drive over to the filling station and I will fill it up with Supremium Bestest Grade gas. And I promise I won't pocket the difference.