Simplify the following text for a Grade 11 native English-speaking person.
Original: Liquefied petroleum gas ( also called LPG , GPL , LP Gas , autogas , or liquid propane gas ) is a flammable mixture of hydrocarbon gases used as a fuel in heating appliances and vehicles .
Simplified: Liquefied petroleum gas ( also known as LPG , LP Gas or autogas ) is a mixture of hydrocarbon gases .