A naturally aspirated engine is an internal combustion engine in which air intake depends solely on atmospheric pressure and which does not rely on air forced through a turbocharger or a supercharger. Many sports cars use naturally aspirated engines due to their lack of a turbo lag. The main advantage of a naturally aspirated engine is they are usually more reliable than turbocharged or supercharged engines. Most automobile gasoline engines, as well as many small engines used for non-automotive purposes, are naturally aspirated. Most modern diesel engines powering highway vehicles are turbocharged to produce a better power-to-weight ratio. They also have better fuel efficiency and lower exhaust emissions.