2021 Subaru Forester: Complete Fluid Specifications

Quick Reference

Fluid	Type/Spec	Capacity
Engine Oil	Subaru Synthetic 0W-20, API SN or SP	4.4 - 5.1 quarts
Engine Coolant	Subaru Super Coolant (Blue)	7.7 - 8.2 quarts
Transmission Fluid	Subaru High-Torque CVT Fluid	Verify in owner's manual
Front Differential	Subaru High Performance 75W-90 Gear Oil	~1.4 quarts
Rear Differential	Subaru High Performance 75W-90 Gear Oil	~0.8 quarts
Brake Fluid	DOT 3 or DOT 4	As needed
Power Steering	N/A (Electric Power Steering)	N/A
Washer Fluid	Any quality washer fluid	~1 gallon

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Getting your fluid services right is the easiest way to ensure a long life for your 2021 Subaru Forester. Using the correct, factory-spec fluid is critical. Modern vehicles are built with tighter tolerances than ever, and using a "universal" or "multi-vehicle" fluid where a specific type is required can lead to premature wear or even catastrophic failure. This guide covers every major fluid your Forester uses, so you can get the job done right, whether you're a DIYer or just want to be more informed when talking to your mechanic.

Engine Oil

Specification: API Conservation Grade SN or SP, 0W-20 Synthetic

Capacity: 4.4 quarts (4.2 liters) for 2.0L FB20 engine, 5.1 quarts (4.8 liters) for 2.5L FB25 engine. Always verify by checking the dipstick after filling.

Notes:

The lifeblood of your Forester's boxer engine is high-quality synthetic oil. Subaru specifies a 0W-20 viscosity for optimal fuel economy and cold-start performance. It is critical to use an oil that meets either API Service SN or the newer API SP classification. These oils provide enhanced protection against low-speed pre-ignition (LSPI), a phenomenon that can occur in modern direct-injection engines.

While Subaru-branded synthetic oil is always a safe bet, any reputable brand that meets the 0W-20 and API SN/SP specs is acceptable. For 2021, Subaru moved to a recommended 7,500-mile or 7.5-month oil change interval under normal driving conditions. However, if you frequently drive in severe conditions (e.g., extreme temperatures, short trips, dusty environments, towing), you should adhere to a shorter interval as outlined in your owner's manual. Never extend oil changes beyond the manufacturer's recommendation.

Engine Coolant

Specification: Subaru Super Coolant (Blue)

Capacity: 7.7 - 8.2 quarts (7.3 - 7.8 liters)

Notes:

Subaru uses a blue, phosphate-based organic acid technology (P-OAT) coolant. This is a long-life coolant, and it is crucial that you only use this specific formulation. Do not mix it with other coolant types, not even other "long-life" or "Asian vehicle" coolants, as this can cause the coolant to gel, leading to blockages in the radiator, heater core, and cooling passages, which can cause severe engine damage. If you are performing a top-off, use only Subaru Super Coolant or an exact P-OAT equivalent (which will also be blue). The factory fill is designed to last for over 10 years or 137,500 miles, but it's wise to inspect its level and condition at every service.

Transmission Fluid

Specification: Subaru High-Torque CVT Fluid (for TR580 and TR690 CVTs)

Capacity: Varies. This is not a simple drain-and-fill service.

Notes:

The Continuously Variable Transmission (CVT) in your 2021 Forester is a highly specialized piece of equipment. It does not use traditional automatic transmission fluid (ATF). You must use the fluid specified for your transmission, which is a high-torque CVT fluid. Using any other type of fluid, including other CVT fluids not specifically formulated for Subaru's high-torque application, will cause damage to the belt and pulleys inside the transmission.

Subaru considers this a "lifetime" fluid under normal driving conditions, but many technicians recommend a drain and fill between 60,000 and 100,000 miles, especially if you tow or drive in mountainous terrain. This is not a DIY-friendly service. The fluid level must be checked at a specific temperature, and there is no dipstick. This service should be left to a qualified technician with the proper equipment.

Front & Rear Differential Fluid

Specification: Subaru High Performance 75W-90 Gear Oil

Capacity: Front: ~1.4 quarts | Rear: ~0.8 quarts

Notes:

Your Forester's Symmetrical All-Wheel Drive system relies on both a front and a rear differential to distribute power to the wheels. These differentials contain their own gear oil, which is separate from the transmission fluid. For the 2021 model year, both the front and rear differentials call for a conventional (non-synthetic) 75W-90 gear oil. While many aftermarket 75W-90 synthetic gear oils exist, it's best to stick with the OEM fluid to avoid any potential issues with seals or performance. Unlike some other vehicles, the Forester's differentials do not typically require a limited-slip additive. This is a relatively easy service, but it requires a fluid pump to get the new oil into the fill hole. Recommended service interval is typically around 30,000 to 60,000 miles.

Brake Fluid

Specification: DOT 3 or DOT 4

Capacity: As needed (typically 1-2 quarts for a full flush)

Notes:

Brake fluid is hygroscopic, meaning it absorbs moisture from the air over time. This moisture lowers the boiling point of the fluid, which can lead to a soft or spongy pedal and reduced braking performance in hard stops. While the system can use either DOT 3 or DOT 4 fluid, DOT 4 has a higher boiling point and is a good upgrade. Never use DOT 5 fluid, as it is silicone-based and incompatible with the system. A full brake fluid flush is recommended every 2-3 years or 30,000 miles, regardless of mileage, to ensure your safety and the longevity of expensive ABS and VDC components.

Power Steering Fluid

Your 2021 Subaru Forester is equipped with Electric Power Steering (EPS). It does not use any power steering fluid, eliminating the need for this service.

Washer Fluid

Specification: Any quality windshield washer fluid

Capacity: ~1 gallon

Notes:

Use any quality washer fluid. In winter months, be sure to use a fluid with a de-icing agent and a low freezing point to prevent damage to the reservoir and pump.

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