I've heard cars described as "durable" but it doesn't mean long operation time. It means that the car is tough and can endure a lot of abuse. For instance, one often hears advertisements for various products which say "durable and long-lasting". "Durable" means tough, resistant to abuse.Durable means the car has long endurance (operation time). Actually, durable or durability is often used in engineering field. But I am not sure "heavy on gas", what does heave mean here?