What is the difference between gear oil 75w90 and 80w90?

[CamilleAnn]

75w-90 and 80W-90 gear oils differ only in viscosity. Below are the viscosity specifications for these two gear oils: 75w-90 viscosity: The kinematic viscosity of 75w-90 gear oil at 100°C is 4.1mm2·s, and the maximum temperature to reach 150Pa·s is -40°C. 80W-90 viscosity: The kinematic viscosity of 80W-90 gear oil at 100°C is 7.0mm2·s, and the maximum temperature to reach 150Pa·s is -26°C.

[Cindy]

As someone who frequently tinkers with vehicles, I believe the main difference between 75W90 and 80W90 gear oils lies in their performance at low temperatures. 75W90 has better low-temperature fluidity, with the "75" after the "W" indicating it can still flow easily at -40°C, making it suitable for cold regions like northern winters where cold starts won't be too difficult. On the other hand, 80W90 becomes somewhat viscous at -26°C, but it's generally fine in milder climates like the south. Both have the same viscosity of 90 at high temperatures, so their protective performance is similar. If you live in an area with significant temperature variations, I'd recommend using 75W90 as it's more versatile. Don't underestimate this difference—using the wrong oil can make it hard to start your car in winter and cause unnecessary delays. I once saw a friend's car make loud gear noises after using the wrong oil, and the issue was only resolved after switching to the right one. So always refer to your vehicle's manual.

[McLane]

I live in an extremely cold winter area and have experienced the difference between 75W90 and 80W90 gear oils. Simply put, the W number represents the oil's flow rate in cold weather: 75W90 is thinner at low temperatures, remaining smooth even at -40°C, making steering and gear shifting smooth without sticking; whereas 80W90 is slightly thicker in the cold, making gears prone to dry grinding below -26°C. In warmer climates, where temperatures stay above freezing year-round, 80W90 is sufficient and more cost-effective. From a practical standpoint, the choice of oil depends entirely on the local climate. Don't forget to check the oil's condition; leaving it unchanged for too long can lead to dirt buildup, affecting lubrication. In severe cold regions, I stick with 75W90 for peace of mind, and there's no need to switch oil types before summer.

[DiIsla]

Having driven for many years and changed various gear oils, the main difference between 75W90 and 80W90 lies in their temperature design. 75W90 flows more easily at low temperatures, making it suitable for cold regions; 80W90 performs well in moderate weather. Choosing the right oil is crucial, otherwise, gears may wear out quickly, leading to higher maintenance costs. It's recommended to regularly check the manual to confirm the correct type.