How Do Diesel Vehicles Work?

Diesel vehicles are similar to gasoline vehicles because they both use internal combustion engines. One difference is that diesel engines typically use a compression-ignited injection system rather than the spark-ignited system used by most gasoline vehicles. In a compression-ignited system, the diesel fuel is injected into the combustion chamber of the engine and ignited by the high temperatures achieved when the gas is compressed. Unlike the emission control systems on gasoline vehicles, many diesel vehicles have an aftertreatment system that reduces particulate matter and breaks down dangerous NOx emissions into harmless nitrogen and water. Diesel is a common transportation fuel, and several other fuel options use similar engine systems and components. Learn about alternative fuel options.

Key Components of a Light-Duty Diesel Vehicle

Aftertreatment system: After the exhaust gas of the engine is filtered through the diesel particulate filter (DPF) and the diesel oxidation catalyst to reduce particulate matter, diesel exhaust fluid (DEF) is injected into the exhaust gas mixture and is reduced to nitrogen and water by chemical conversion within the selective catalytic reducer (SCR) before being released into the atmosphere via the vehicle's tailpipe.
Battery: The battery provides electricity to start the engine and power vehicle electronics/accessories.
Diesel exhaust filler: This port is for filling the diesel exhaust fluid tank.
Electronic control module (ECM): The ECM controls the fuel mixture, ignition timing, and emissions system; monitors the operation of the vehicle; safeguards the engine from abuse; and detects and troubleshoots problems.
Fuel filler: This is a filler or "nozzle" used to add fuel to the tank.
Fuel line: A metal tube or flexible hose (or a combination of these) allows for transferring fuel from the tank to the engine's fuel injection system.
Fuel pump: A pump that transfers fuel from the tank to the engine's fuel injection system via the fuel line.
Fuel tank (diesel): Stores fuel on board the vehicle until it's needed to power the engine.
Internal combustion engine (compression-ignited): In this configuration, fuel is injected into the combustion chamber and ignited by the high temperature achieved when a gas is greatly compressed.
Transmission: The transmission transfers mechanical power from the engine and/or electric traction motor to drive the wheels.


  • Biodiesel car image
  • Natural gas car image
  • Bifuel natural gas car image
  • Propane car image
  • Bifuel propane car image