Most gas stations stock three grades of fuel, which are listed by their octane level: 87 (regular/unleaded), 89 (plus) and 91 (premium). Check your car manual to see what gas the manufacturer requires for your car. Using a lower grade than required may lead to costly engine repairs in the future. Under no circumstances should you use diesel fuel in a gasoline engine.
The recommended gasoline for most cars is regular, and using premium gasoline will offer no benefit. It won't make your car perform better, go faster, get better mileage, or run cleaner.
This article originally appeared on YourMechanic.com as What Type of Gas Should I Use? and was authored by Maddy Martin.