What does 85w90 mean for transmission oil?

[SanJasmine]

Transmission gear oil 85w90 is a viscosity grade designation. The 'W' in the viscosity grade designation of gear oil stands for winter-type gear oil. The number before the 'W' indicates the low-temperature viscosity, where a smaller number means lower viscosity, better fluidity, and stronger low-temperature performance. The number after the 'W' indicates the high-temperature viscosity, where a larger number means higher high-temperature viscosity and the ability to withstand higher temperatures. The types of transmission oil are as follows: Transmission oil is generally divided into three types: manual transmission oil, automatic transmission oil, and continuously variable transmission oil. Manual transmission oil is commonly known as gear oil. Automatic transmission oil is commonly known as gearshift oil (ATF). Continuously variable transmission oil is commonly known as traction oil (CVTF). The functions of transmission oil are as follows: Reduce friction, minimize wear, and control the friction of the clutch and the performance of the synchronizer. Load-bearing (low-speed high torque, vibration load), heat dissipation, vibration and noise reduction, and removal of contaminants at gear meshing points (cleaning function). Prevent corrosion, pitting, and surface metal tearing, isolate metal surfaces, and prevent direct contact between metal bodies.

[OAshley]

The transmission oil 85W90 is a viscosity grade, just like how we carefully choose engine oil. The 'W' in 85W stands for winter low-temperature fluidity, and the lower the number, the better it is for cold starts in frigid regions. Last time I helped my neighbor change his oil, his old Jetta used this grade because 85W can still flow smoothly at temperatures below minus ten degrees Celsius, preventing gear shifting issues in winter. The 90 represents the high-temperature viscosity value, ensuring stable oil film protection for gears during long summer drives to prevent wear. But don't assume it's universally suitable—many newer cars now use 75W90, which has lower viscosity and better fuel efficiency. Always follow the manufacturer's manual when selecting oil; using the wrong oil in a manual transmission can lead to rough shifting or even gear grinding. Remember to check the oil condition every 50,000 kilometers.

[SanNoah]

Back when I worked on cars, I often explained to apprentices the meaning of gear oil grades like 85w90. The 85W indicates that the oil maintains fluidity at around -12°C, making it suitable for northern car owners during cold winter starts—unlike low-grade oils that can turn into paste. The 90 represents the viscosity parameter at high temperatures, ensuring the oil film doesn't break under high-speed gear operation. This grade is commonly used in manual transmissions and rear differentials, but it should never be used in automatic transmissions. Just last week, a customer tried to save money by using the wrong oil, resulting in transmission slippage and strange noises. Older cars with larger metal gaps benefit from 85w90, but for precise modern transmissions, lower-viscosity oils like 75w85 are recommended—they save fuel and run quieter.

[AnnaMarie]

85w90 is actually a dual viscosity standard for gear oil, and choosing it depends on regional climate. When I was doing long-distance transportation, I specifically researched it. 85W is suitable for regions above -15 degrees Celsius, and it starts much faster in cold winters compared to regular single-grade oil. The high-temperature viscosity of 90 is particularly important in the scorching summers of the south, protecting gears from high-temperature wear. However, vehicle owners in high-altitude mountainous areas should note that at higher altitudes with lower temperatures, 75w90 might be more appropriate. Additionally, vehicle usage is also crucial. I use 85w90 for my pickup truck hauling loads because it's thicker and more wear-resistant than oil for sedans. During every maintenance, keep an eye on the oil color—if it turns black or emulsifies, it's time to change it. Don't wait until the transmission starts making noise to take action.