The main difference between 80W90 and 85W90 gear oil is their viscosity. 80W90 gear oil has a viscosity rating of 80W at low temperatures, while 85W90 gear oil has a viscosity rating of 85W at low temperatures. This means that 80W90 gear oil is thicker than 85W90 gear oil at low temperatures.
The thicker viscosity of 80W90 gear oil can make it more difficult for your transmission to shift gears. This is especially true if you have a manual transmission. If you do use 80W90 gear oil in a manual transmission, you may need to shift gears more slowly and smoothly.
The thicker viscosity of 80W90 gear oil can also cause your transmission to run hotter. This is because the thicker oil creates more friction between the gears. If you use 80W90 gear oil in a transmission that is not designed for it, you may need to monitor the transmission temperature and make sure that it does not overheat.
In general, it is best to use the type of gear oil that is recommended by the manufacturer of your vehicle. If you are not sure what type of gear oil to use, you can consult with a qualified automotive technician.
