The STI’s 6-speed manual gearbox and driver-controlled center differential are engineered for performance, meaning they require the correct amount of high-quality gear oil to stay smooth, cool, and protected.
STI Transmission Fluid Capacity
Most STI transmissions hold 3.7 to 4.3 quarts (3.5 to 4.1 liters) of gear oil, depending on the model year, with the rear differential holding about 1–1.1 quarts.
Keeping the fluid fresh prevents gear wear, notchy shifting, and overheating, problems that can be expensive to repair if ignored.
| STI Model Year | Transmission Fluid Capacity (Quarts / Liters) | Rear Differential Fluid Capacity (Quarts / Liters) |
|---|---|---|
| 2004 GD | 3.7 qt (3.5 L) | 1.0 qt (0.95 L) |
| 2005 GD | 3.7 qt (3.5 L) | 1.0 qt (0.95 L) |
| 2006 GD | 3.8 qt (3.6 L) | 1.0 qt (0.95 L) |
| 2007 GD | 3.9 qt (3.7 L) | 1.0 qt (0.95 L) |
| 2008 GR | 4.0 qt (3.8 L) | 1.0 qt (0.95 L) |
| 2009 GR | 4.0 qt (3.8 L) | 1.0 qt (0.95 L) |
| 2010 GR | 4.1 qt (3.9 L) | 1.0 qt (0.95 L) |
| 2011 GR | 4.1 qt (3.9 L) | 1.1 qt (1.05 L) |
| 2012 GR | 4.2 qt (4.0 L) | 1.1 qt (1.05 L) |
| 2013 GR | 4.2 qt (4.0 L) | 1.1 qt (1.05 L) |
| 2014 GR | 4.2 qt (4.0 L) | 1.1 qt (1.05 L) |
| 2015 VA | 4.1 qt (3.9 L) | 1.1 qt (1.05 L) |
| 2016 VA | 4.2 qt (4.0 L) | 1.1 qt (1.05 L) |
| 2017 VA | 4.2 qt (4.0 L) | 1.1 qt (1.05 L) |
| 2018 VA | 4.3 qt (4.1 L) | 1.1 qt (1.05 L) |
| 2019 VA | 4.3 qt (4.1 L) | 1.1 qt (1.05 L) |
| 2020 VA | 4.3 qt (4.1 L) | 1.1 qt (1.05 L) |
| 2021 VA | 4.3 qt (4.1 L) | 1.1 qt (1.05 L) |
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2004–2007 WRX STI (GD)
- Capacity: 3.7–3.9 quarts
- Recommended fluid: 75W-90 GL-5 synthetic
2008–2014 WRX STI (GR/GV)
- Capacity: 4.0–4.2 quarts
- Known for improved shift feel compared to the GD
2015–2021 WRX STI (VA)
- Capacity: 4.1–4.3 quarts
- Subaru factory fill: high-performance 75W-90 GL-5 gear oil
Rear Differential (All STI Generations)
- Capacity: 1–1.1 quarts
- Fluid type: GL-5 gear oil
- Some models require friction modifiers depending on the limited-slip differential type.
Related Transmission Fluid Viscosity Chart(For All Fluid Types)
Recommended Transmission Fluids for STI
Choosing the correct gear oil enhances shift quality and protection. Popular synthetic options include:
- Motul Gear 300 75W-90
- Red Line 75W90NS
- Subaru Extra-S
These oils resist heat, reduce gear chatter, and offer excellent longevity under heavy load.
How to Check STI Transmission Fluid Level
Checking the fluid level is simple:
- Warm the car fully.
- Park on a level surface.
- Locate the transmission dipstick on top of the gearbox.
- Pull it out, wipe clean, reinsert, and check again.
- Add fluid slowly if below the Full line.
Never overfill, it can cause aeration, foaming, or leaks.
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How to Change STI Transmission Fluid
Changing the fluid is a DIY-friendly job:
- Lift the car safely.
- Remove the transmission drain plug and drain the oil.
- Replace the crush washer and reinstall the plug.
- Refill through the dipstick tube using a long funnel.
- Verify the fluid level and test drive.
If shifting remains notchy after a fluid change, the issue may involve worn synchros or clutch components.
Common Problems Caused by Incorrect Fluid Levels
Running the wrong amount of gear oil can cause:
- Hard shifting
- Gear grinding
- Whining or humming noises
- Overheating
- Premature synchro and bearing wear
Too little fluid starves components of lubrication, while too much can cause pressure buildup and leaks.
Temperature and Performance Considerations
Gear oil thickens in cold weather, causing stiff shifting until it warms. High-quality synthetics help minimize this. In hot climates or track conditions, better fluid formulas reduce heat buildup and maintain smoothness under stress.
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FAQs
How much transmission fluid does a 2004 STI use?
The 2004 Subaru WRX STI 6-speed manual transmission holds approximately 3.7 quarts (3.5 liters) of gear oil. The rear differential requires about 1 quart (0.95 liters).
How to check STI transmission fluid?
- Warm up the car and park on a level surface.
- Locate the transmission dipstick on top of the gearbox.
- Pull out the dipstick, wipe it clean, reinsert it, and then pull it out again to read the level.
- Add fluid slowly if the level is below the “Full” mark.
How much transmission fluid does a Subaru take?
Most modern Subaru manual transmissions take between 3.7 and 4.3 quarts (3.5–4.1 liters), depending on the model year. Rear differentials generally hold about 1 to 1.1 quarts.
When to change transmission fluid Subaru STI?
Subaru recommends changing the STI transmission fluid every 30,000–50,000 miles, though performance drivers often change it every 15,000–25,000 miles for optimal gearbox protection.
How much transmission fluid does a 2003 Subaru Legacy take?
A 2003 Subaru Legacy manual transmission typically holds about 2.7–3.0 quarts (2.6–2.8 liters) of gear oil. Check the owner’s manual for exact specifications, as it varies by trim and drivetrain.
How much oil does a STI take?
If you mean engine oil, most Subaru STI engines hold approximately 4.9–5.0 quarts (4.6–4.7 liters) with a filter change. Always use the grade recommended in the owner’s manual.
How to read STI dipstick?
- Remove the dipstick and wipe it clean.
- Reinsert fully, then pull it out again.
- Read the fluid level between the “Low” and “Full” marks.
- Ensure the car is on a level surface, and the transmission is at operating temperature for accurate measurement.
Final words
Knowing your STI transmission fluid capacity and maintaining it regularly ensures your 6-speed gearbox stays strong, smooth, and reliable. With capacities ranging from 3.7 to 4.3 quarts, depending on model year, and about 1 quart for the rear differential, staying on top of fluid changes is a simple way to protect your STI’s performance.
Whether you daily drive your STI or push it on the track, proper transmission fluid maintenance keeps the legendary drivetrain performing at its best.
