Premium fuel gives your gas mileage a boost
Myth: Putting premium fuel in your vehicle, even when it doesn't require it, will give your gas mileage a boost.
It may seem like premium fuel equates to better fuel economy, but you won't see even the tiniest jump in your mpg by using premium fuel in a vehicle that's designed for regular.
In fact, it's just a waste of money, Molla says. Premium will cost you about 15 to 20 cents more per gallon, which can add up to $100 or more per year over time, according to the Federal Trade Commission.
In addition, "Using a higher-octane fuel than is recommended will have no effect on performance or fuel economy," Molla says.
How to save: The FTC says that unless it's recommended by your owners manual, don't spend money on higher-octane gas.