| C-4 | Allison ATF specification |
| CAM | Camshaft |
| CAN | Controlled Area Network |
| CARB | Carburator |
| CASE | Cranking Angle Sensing Error |
| CC | Cubic Centimetre |
| CC | Climate Control |
| CC | Cruise Control |
| CCC | Computer Command Control |
| CCD | Combustion Chamber Deposits |
| CCLF | Camera Controlled Lighting Functions |
| CCM | Central Control Module |
| CCM | Chassis Control Module |
| CCMC | Comité des Constructeurs d’Automobiles du Marché Commun (predecessor of ACEA) |
| CD | Coefficient of Drag |
| CD-2/CF-2 | API 2-stroke diesel engine oil specification |
| CEFIC | Conseil Européen des Federations de l’Industrie Chimique (European Chemical Industry Council) |
| CEN | Conseil Européen de Normalisation |
| CES | Cummins Engineering Specification |
| CFC | Chlorinated Fluorocarbon |
| CFI | Cold Flow Improver |
| CFI | Central Fuel Injection (replaced with TBI) |
| CFI | Continuous Fuel Injection |
| CFM | Cubic feet per minute |
| CFPP | Cold Filter Plugging Point |
| CFR | Coordinating Fuel and Equipment Research Committee |
| CFV | Clean Fuel Vehicle |
| CG | Conventional Gasoline |
| CGO | Cracked Gas Oil |
| CH4 | API heavy-duty engine oil specification |
| CI | Cetane Index |
| CI | Compression Ignition |
| CID | Cubic Inch Displacement |
| CIDI | Compression Ignition Direct Injection (diesel) |
| CIMAC | Congrès International des Machines à Combustion |
| CKP | Crankshaft Position |
| CKT | Circuit |
| CL | Closed Loop |
| CLC | Converter Lockup Clutch (replaced with TCC) |
| CLNT | Coolant |
| CM | Cincinnati Milacron |
| CMA | Chemical Manufacturers Association |
| CMAQ | Congestion Mitigation and Air Quality Improvement Program |
| CMFI | Central Multi-port Fuel Injection |
| CMP | Camshaft Position |
| CN | Cetane Number |
| CNG | Compressed Natural Gas |
| CO | Carbon Monoxide |
| CO2 | Carbon Dioxide |
| COC | Cleveland open cup |
| cP | Centipoise |
| CPC | Camshaft Position Control |
| CPI | Central Port Fuel Injection |
| CPS | Central Power Supply |
| CPU | Central Processing Unit |
| CR | Common Rail (diesel injection) |
| CRD | Common Rail Diesel |
| CRDPF | Continuously Regenerating Diesel Particulate Filter |
| CRT | Cathode Ray Tube |
| CRTS | Continuously Regenerating Trap System |
| CSFI | Central Sequential Fuel Injection |
| CSM | Central Security Module |
| cSt | Centistokes |
| CSTCC | Continuously Slipping Torque Converter Clutch |
| CTOX | Continuous Trap Oxidizer |
| CV | Constant Velocity (joints) |
| CVRSS | Continuously Variable Road Sensing Suspension |
| CVRTD | Continuously Variable Real Time Damping |
| CVT | Continuously Variable Transmission |
| CZS | Crash Zone Sensor |
