(CNN) -- More expensive gas does not necessarily mean better quality.
That's according to a new study.
AAA, The American Automobile Association -- says 'premium' gas may not always live up to the hype.
They tested regular and premium fuel in vehicles designed to run on regular gas.
According to their research, only some engines notice benefits like a horsepower boost and better fuel economy.
For most cars, there's no difference.
AAA recommends if you use regular fuel use the ones labeled "top tier" to reduce engine deposits.
Bottom line: If your vehicle actually requires premium fuel, stick to that guideline.
But for others, you may be wasting your money.