How to Choose Transmission Fluid for Your Car?

[VonRose]

Transmission fluid should be selected based on the type of transmission. Car transmissions are divided into MT, AT, AMT, CVT, DCT, etc., and the fluids for different transmissions cannot be mixed. The details are as follows: Manual (MT) Transmission: Manual (MT) transmissions use gear oil, which primarily serves to lubricate and dissipate heat. It is categorized into five grades based on quality, with GL4 and GL5 generally available in the market. In terms of characteristics, manual transmission fluid is more viscous than automatic transmission fluid and typically requires more frequent replacement. AMT Transmission: AMT transmissions can generally use MT transmission fluid. Their working principle is an improvement over manual transmissions (MT), mainly altering the manual gear-shifting mechanism. By adding a microcomputer-controlled automatic shifting system without changing the overall transmission structure, AMT transmissions can share the same transmission fluid as MT. AT Transmission: AT transmission fluid is specifically designed for automatic transmissions. It serves two purposes: lubricating and cooling the planetary gear set, and most importantly, transmitting power, which is why it is less viscous than manual transmission fluid. AT transmissions now mainly include 4AT, 5AT, 6AT, 7AT, 8AT, and 9AT, each requiring different transmission fluid models. The more gears a transmission has, the higher the requirements for the AT transmission fluid.

[OEliana]

I remember the first time I picked transmission fluid myself, I was completely clueless and ended up buying a cheap generic one. The car drove like it was drunk, shaking all over the place. Later, I consulted an experienced mechanic and learned that each car's transmission requires a specific fluid type, which must be found in the user manual—whether it's ATF Dexron for automatics or GL-4 for manuals. The manual clearly states the viscosity grade and compatible brands. Don’t try to save money by buying random fluids; good oil protects internal gears for smooth operation. Regular fluid changes are also crucial, typically every 50,000 to 100,000 km depending on driving habits—sooner if you do a lot of highway driving. Since then, I’ve stuck to the manual’s recommended OEM or premium brands like Mobil, and the car runs much smoother, with the transmission lasting years longer.

[ElliotAnn]

As a friend who just bought a car, I’ve also been confused. The first step in choosing transmission oil is to check the user manual—it acts like a navigation map, specifying the type and specifications of the oil. Automatic cars use ATF like Mercon V, while manual cars use thicker GL-class oils. If you don’t have the manual, check online forums or ask a 4S technician. The second step is to buy a compatible brand product, such as Shell or Castrol, ensuring the packaging indicates the compatible model. The oil change interval is generally 60,000–80,000 km, but it may shorten to 50,000 km in heavy traffic. Remember not to mix different types of oil or confuse manual and automatic transmissions, as the wrong choice may cause gear-shifting issues or overheating. A simple strategy is to let the manual guide you—it’s worry-free and reliable.

[SanWyatt]

From a technical perspective, the key to transmission fluid selection lies in component compatibility. Automatic Transmission Fluid (ATF) relies on specific friction modifiers and viscosity control for gear synchronization - Japanese vehicles commonly use ATF+4 while American models prefer Dexron. Manual transmission fluids are more viscous, with GL-5 being suitable for high-load driving. Owner's manuals specify viscosity grades like 75W-90, while additives prevent oxidative wear. Choosing inferior quality oil may cause hydraulic failure or internal corrosion. Regular fluid changes optimize gear lubrication efficiency, prolong component lifespan, and ensure precise responsiveness.