What is the difference between unleaded, regular, super and diesel?

What is the difference between unleaded, regular, super and diesel?

James Bell (Publisher, Auto Reviewer) gives expert video advice on: What does "total" mean on the sticker price?; What is a "test drive"?; What is the difference between unleaded, regular, super and diesel? and more...

Fuel economy is usually referenced by the EPA rating, or the city and highway miles per gallon that you can expect in normal driving. Unleaded and super unleaded gasoline are two different grades of gasoline and it's in reference to its octane rating. The only reason to put a super unleaded or a higher octane fuel in your vehicle is if it's stated in the actual owner's manual of the car because the vehicle has been built to such a specification that it requires that additional octane to run correctly. Diesel fuel is actually a completely different concoction that's much more oil-based. This is used in diesel vehicles, most often in trucks, semi tractor trailers and larger vehicles, but it is becoming more popular and common in passenger vehicles as well. Essentially you need to make sure that you never mix diesel fuel into a vehicle that's due to run on gasoline, and vice versa, because the two are very damaging to the wrong sort of engine.