Can I Use 75W-90 Instead Of 75W-85?

Gear oil is important for the transmission system of a vehicle to work properly. It ensures the proper lubrication required for the system’s smooth and effective operation. The viscosity, or thickness, of the gear oil is an important consideration when choosing the proper gear oil for a vehicle.

The two most frequent viscosities for gear oil are 75W-85 and 75W-90. While 75W-85 is the most widely used gear oil, 75W-90 can be substituted in some situations. Some GM dealers use 75W-90 gear lube in applications where Chevrolet/Buick/GMC/Cadillac recommends 75W-85.

75W-90 gear oil has a greater viscosity than 75W-85, indicating that it is more viscous and provides superior lubrication. This makes it an excellent option for older vehicles with heavy mileage, since the increased viscosity prevents transmission system wear and tear. Additionally, 75W-90 gear oil is an excellent option for cars that are frequently exposed to harsh temperatures, since its higher viscosity prevents overheating.

Therefore, it is safe to conclude that 75W-85 gear oil can be substituted for 75W-90, particularly when the vehicle is older, has a high mileage, or is frequently exposed to harsh temperatures. Check your owner’s handbook or with a reputable mechanic to ensure that the gear oil you are using is appropriate for your car.


Cars were and will be my first love and favorite hobby; I decided to start writing about my discoveries and techniques to improve my cars or repair them.