The most popular, the most viscosity, the most applications. 75W90 GL-4 gear oil (similar to SAE 5W40/10W40 engine oil viscosity) Popular in Nissan, Mazda, Mitsubishi, VW/Audi, Lotus Elise/Exige, Toyota, Mendeola transmissions and Atlas transfer cases for Off Road Offers quicker shifts, perfect synchronizer coefficient of friction Safe for brass synchros, as it lacks the reactive sulfurs found in most GL-5 oils that cause damage High performance gear protection and longer synchro life Eliminates notchy shifting, even when cold Satisfies the gear oil viscosity requirements of 75W90, 80W90, 90 and motor oil viscosities of SAE 40, 10W40 and 15W40 Recommended for GL-1, GL-3 and GL-4 applications, as well as where most special synchromesh fluids are specified
Since most GL-5 gear oils for differentials are too slippery for manual transmissions, Red Line offers these products that ensure proper shifting while providing ultimate wear protection
| API Service Class | GL 4 |
| SAE Viscosity Grade (Gear Oil) | 75W90 |
| SAE Viscosity Grade (Motor Oil) | 15W40 |
| Vis @ 100°C, CSt | 15.5 |
| Vis @ 40°C, CSt | 86 |
| Viscosity Index | 194 |
| Pour Point, °C | -45 |
| Pour Point, °F | -49 |
| Brookfield Viscosity @ -40°C, Poise | 320 |