Q: How Are Diesel and Gasoline Engines Different?

There are two main differences between gasoline and diesel engines. Gasoline engines use gasoline for fuel and spark ignition to ignite the fuel. Diesel engines use diesel fuel and compression for ignition to ignite the fuel. There are also many minor differences between how the two engines work.

The gasoline engine uses lighter duty engine components since the gasoline engine usually has lower compression and will produce less horsepower and torque. The gasoline engine has an electronic ignition and spark control. Gasoline engines use a throttle body with a throttle cable or electronic actuator to control the opening of the throttle plates that control the air going into the engine. The fuel is injected into the intake air flow on most engines and some have a direct injection system to inject high pressure into the cylinder directly. Once the mixture is compressed, it is ignited using a spark plug. The result is a power stroke.

A diesel engine uses heavier duty components due to the higher compression and heat the engine produces. The air goes into the intake through a diaphragm type spring valve plate in the intake and engine speed is controlled by injected amounts of fuel via an injection pump. The diesel fuel is injected into the cylinder head small cup area and the compression of the engine ignites the fuel and air in the cylinder when the piston reaches top dead center. Diesel fuel will produce more power than gasoline and most diesel engines will produce more torque than a same size gas engine will. The diesel engine will use glow plugs to preheat the cylinder head cup to help ignite the fuel in cold temperatures, which is a problem that a gas engine does not have in most temperatures. Diesel engines will weigh almost twice as a gasoline engine with the same displacement. Diesel engines are designed for heavy duty work loads and in most cases will outlast a gasoline motor.

When it comes to choosing a gasoline or a diesel motor it should come down to what kind of work the engine will be doing, rather than personal preferences. A gasoline motor runs quieter and smoother, while a diesel engine is noisy and runs smoother above idle. A diesel engine is more common in trucks and large cars where they carry heavier loads better than gasoline engines for long term use.