- By-pass Valve
- A general term for a valve that lets liquid or air circumvent a filter. For example, an oil bypass valve allows oil to circulate when the oil filter is clogged
- Cabriolet
- Another term for a convertible. European manufacturers often call convertible models Cabriolets or Cabrios.
- Camshaft
- A machined shaft with lobes that opens and closes engine cylinder valves. The crankshaft drives the camshaft through gears, belts, or chains.
- Carburetor
- A device that mixes fuel and air to provide a combustible mixture. Air blowing over the fuel nozzles(jets) results in an air-fuel mixture burned in the cylinders. Carburetors were common on most vehicles before 1985. Currently, most vehicles use some form of fuel injection instead.
- Clutch
- A mechanism that uses plates coated with a high-friction material to transfer power. Clutches are also used to isolate rotating and non-rotating components. Clutches can allow slip between components to reduce shock loads between rotating and stationary components. Manual transmission vehicles use a clutch to transfer power from the gearbox to the wheels. Air conditioning compressors use clutches as well.
- Coil Spring
- A spring composed of hardened steel spiral wound used to isolate a vehicle from the road. Coil springs are preferred over leaf springs for their superior ride and control.
- Concours d'Elegance
- A French term that describes an auto show of classic and vintage cars
- Constant Velocity Joint
- A shaft that transmits engine power from the transmission to the wheel. CV joints allow the wheel to steer and follow suspension motion while receiving power. CV joints are used in front-wheel drive, rear-wheel drive, and all-wheel drive vehicles.
- Cowl
- A protective cover for mechanical components. Often used for engines, fans, etc.
- Cowl Shake
- The vibration and "flutter" of the hood (cowl) of a convertible when traversing bumps and other road imperfections
- Crankshaft
- The shaft that converts the linear motion of the pistons into rotation. The crankshaft is connected to the transmission.
- Curb Weight
- The total weight of the automobile with a full tank of fuel, and all other fluids.
- Differential
- A differential allows the right and left wheels to rotate at different RPM. This is necessary because as a car goes around a curve, the outside wheel rotates faster than the inside wheel to "keep up". The differential allows the outside wheel to spin faster to compensate for the greater distance it travels.
- Distributor
- A device that transfers voltage to the spark plug. A rotor in the distributor spins and touches contacts that are connected to spark plug wires. The wires then conduct the voltage to the spark plug.
- DOHC
- Acronym for dual/double overhead cam (see Overhead Cam)
