The pitch: Higher octane will improve your car’s performance and make it run better.
The truth: Car and Driver magazine conducted an extensive study and found that for all but the most high-performance cars, putting high-test into your tank burns nothing but cash. According to the American Automobile Association, there’s about a 25-cent difference per gallon, or about $4.50 per fill-up if you have an 18-gallon gas tank.
The exception: If you own a Ferrari. (And if you do, what are you doing reading this? Go help the economy by buying something!)