Diesel/ˈdiːzl/ Definition 1 of 3Pro Tip 1/3Not for Petrol Diesel is different from petrol; using it in a petrol engine can cause damage. Remember, your car needs petrol, not diesel. Pro Tip 2/3Fuel Efficiency Diesel engines are often more fuel-efficient than petrol engines. Diesel cars can travel longer distances on less fuel. Pro Tip 3/3Heavy Machinery Diesel is common in trucks, buses, and heavy machinery due to its durability. Most heavy trucks on the road have diesel engines.