| UEIL | Union Européenne des Indépendants en Lubrifiants |
| UFIP | Union Française des Industries Pétrolières |
| UHC | Unburnt Hydrocarbon |
| UL | Unleaded Gasoline |
| ULEV | Ultra Low-Emission Vehicle |
| ULSD | Ultra Low Sulfur Diesel |
| ULSK | Ultra Low Sulphur Kerosene |
| UNI | Ente Nazionale Italiano di Unificazione (Italian organization for standardisation) |
| USS | US Steel |
| UTAC | Union Technique de l’Automobile, du Motocycle et du Cycle (F) |
| UTF | Universal Tractor Fluid |
| UTTO | Universal Tractor Transmission Oil |
| UV | Ultraviolet |
