Which is smoother, 75W80 or 75W90 transmission fluid?
2 Answers
Transmission fluid 75W90 has higher viscosity and better stickiness, making it more effective. Generally, 75W-90 is suitable for all seasons in most vehicles. Here are detailed introductions about automotive transmissions: 1. Overview: The transmission is a device that changes the speed ratio and direction of motion, usually located between the clutch and the central drive. It can alter the torque, speed, and direction of motion transmitted from the driving shaft to the driven shaft under different working conditions. Gear-driven transmissions typically consist of a housing and several gears. 2. Classification: Automatic transmissions have become mainstream internationally, mainly including AT, AMT, CVT, and DCT types. The early transmission systems of AT transmissions were mainly 4AT. AT achieves automatic shifting through an electronically controlled automatic operating system. CVT is a true continuously variable transmission with fewer parts and a smaller size. DCT has two clutches.
I'm the type who enjoys delving into automotive details, and the viscosity difference in transmission fluid directly impacts shift smoothness. The 'w' in 75w80 and 75w90 stands for winter low-temperature performance—both perform similarly in smoothness during cold starts. However, at high temperatures, 80 has lower viscosity (thinner oil), resulting in more fluid and flexible shifts for a smoother feel. In contrast, 90's higher high-temperature viscosity means slightly thicker oil, offering better protection under heavy loads or high-heat conditions, though it may feel less smooth during frequent stop-and-go driving. The key lies in your vehicle's manual specifications—some transmissions are designed exclusively for either 80 or 90, and misuse can accelerate wear or cause noise. I recommend first consulting the manual for the correct match. For daily driving in moderate climates, 75w80 may deliver smoother shifts, but always verify fluid quality to avoid counterfeit products. Overall smoothness also depends on driving habits, such as aggressive acceleration versus steady cruising.
