diesel engine: An engine that burns diesel fuel instead of gasoline.

diesel fuel; diesel oil: Fuel for cars with diesel engines. It’s similar to home heating oil, kerosene, and jet fuel.

dipstick: A metal stick that’s inserted into a reservoir to check the level of the fluid in the reservoir by means of markings on the stick. The most common dipsticks check the levels of engine oil, transmission fluid, and power-steering fluid.

disc brakes: Brakes that have calipers with high-friction brake pads, which grab a brake disc (sometimes called a rotor) attached to the wheel and force it to stop turning, thus stopping the car.

distributor: The part of the ignition system that distributes the proper amount of electrical voltage to each spark plug in the correct sequence. This task is now performed electronically on distributorless ignition systems.

distributor cap: A cap that over the distributor that has an outlet for each spark plug wire, plus an outlet where the wire from the ignition coil enters the cap to conduct high-voltage electrical current to the rotor.

drive train: The path of power from the engine to the drive wheels. Consists of the clutch, transmission, driveshaft, differential, and the axle on which the drive wheels are situated.

drum brakes: Brakes that use hydraulic pressure to force curved brake shoes against the inner walls of a hollow metal drum attached to each wheel.