Octane. You see the word every time you visit the gas station but what does it mean? Octane ratings measure fuel's ability to resist engine knock. Engine knock is caused by fuel being ignited by something other than the spark plug.
If you are using an octane grade that is too low for your vehicle, something other than the spark plug can ignite the fuel in the engine. The engine could even get hot enough where the fuel explodes by itself.
What octane does your vehicle require? Check your vehicle's owner's manual. Don't upgrade to more expensive octane ratings unless your manufacturer recommends it.