What Is Transmission Fluid And Why Is It Important?
Your Subaru comes with many different types of fluids: motor oil, coolant, and so on. Transmission fluid is one of the lesser known fluids. Yet, it’s just as important as the other fluids that keep your car running.
What Is Transmission Fluid?
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Transmission fluid is used for automatic and manual transmissions. It's a red or green fluid that circulates in the transmission. It runs through the:
- Transmission (torque converter pump)
- Transmission cooler lines
- Transmission cooler within the radiator
Transmission fluid comes has many different components. The most common ones include:
- Base oil
- Additives
- Anti-wear additives
- Rust inhibitors
- Detergents
- Other additives that optimize the fluid’s performance within a certain transmission
Why Your Subaru Has Transmission Fluid
The primary purpose of transmission fluid is to lubricate the transmission. If you have an automatic transmission, the fluid also acts as a coolant. It reduces high operating temperatures within the transmission. The fluid also cleans and protects the metal surfaces within the transmission from wear. The fluid also conditions the gaskets and seals to keep them working well.
Without transmission fluid, your transmission gears would grind against each other. Low transmission fluid can cause the transmission to overheat. Transmission fluid is necessary for the smooth operation of the transmission.
Transmission Fluid Has Other Purposes Too
Depending on the type of transmission fluid you use, it may serve other purposes within your vehicle. For example, ATF-HP transmission fluid isn't only for transmissions. It can also be a:
- Hydraulic fluid in some power steering systems
- If you're looking for Subaru transmission fluid for power steering, get ATF-HP (only if it's compatible with your transmission)
- Lubricant in some 4WD transfer cases
- Lubricant in some modern manual transmissions
Transmission fluid may be the most versatile fluid in your vehicle.
Which Subaru Transmission Fluid Type To Put Into Your Vehicle
Each type of transmission needs a certain type of transmission fluid. There are many types on the market because each transmission has special requirements for many different areas. For example, valve operation, gear lubrication, torque converter operation, and more. There's no "universal" transmission fluid.
It’s important to get the right fluid for your Subaru’s transmission. As a general rule of thumb, you should put:
- ATF-HP transmission fluid into 2005+ Subaru vehicles (except those with CVT transmissions)
- DEXRON III transmission fluid into 2004 and earlier Subaru vehicles
When in doubt, check your owner’s manual for the right Subaru transmission fluid type.
How Long Does Transmission Fluid Last?
Transmission fluid doesn’t last forever. It degrades, or wears out, over time. When it is degraded enough, it can’t do its job as well anymore. The change interval depends on your car. For many older cars, it is recommended to change the fluid every 30K miles. For some newer vehicles, the recommendation is to change the fluid every 100K. Change intervals are getting longer as both fluid and transmission designs improve. Consult your owners manual to find the correct change interval. The longevity of your transmission fluid depends on several factors, including:
- Your driving habits
- Whether or not you tow often
- The state of your transmission
- The type of vehicle you have
Here are some resources on checking and replacing your transmission fluid:
Do you have any questions about the transmission fluid in your Subaru? Feel free to contact us!