2021 Subaru Outback Coolant Capacity & Type

The 2021 Subaru Outback cooling system holds approximately 7.6 to 7.9 US quarts (7.2 to 7.5 liters) of coolant, depending on the specific engine.

Quick Answer

• Total Cooling System Capacity: 7.6 - 7.9 US Quarts (7.2 - 7.5 Liters)
• OEM Coolant Specification: Subaru Super Coolant (Blue, Phosphated Organic Acid Technology - POAT, p/n SOA868V9270). This is a 50/50 pre-mixed solution.
• Mix Ratio: 50/50 pre-mixed (do not dilute further if using Subaru Super Coolant).

Capacity by Engine Option

Flush Interval

Subaru recommends a significantly longer flush interval for their Super Coolant compared to conventional coolants.

• Normal Duty: Initial replacement at 137,500 miles (220,000 km) or 11 years, whichever comes first. Subsequent replacements every 75,000 miles (120,000 km) or 6 years.
• Severe Duty: While Subaru's Super Coolant offers extended life, certain severe conditions (e.g., frequent towing, extreme climates, extensive off-road use) may warrant more frequent inspection, but the main flush interval generally remains the same due to its long-life properties.

How to Refill & Bleed

Properly refilling and bleeding the cooling system of your 2021 Subaru Outback is critical to prevent air pockets, which can lead to overheating.

1. Preparation: Ensure the engine is cool. Position the vehicle on a level surface. Wear appropriate safety gear (gloves, eye protection).
2. Drain (if flushing): Open the radiator drain cock and remove the radiator cap to allow the system to drain. Some models may have an additional drain plug on the engine block. Collect used coolant in an appropriate container for recycling.
3. Close Drains: Once drained, close the radiator drain cock and reinstall any engine block drain plugs.
4. Refill: Slowly pour the correct Subaru Super Coolant (50/50 pre-mixed) into the radiator. Fill until the coolant reaches the top of the filler neck.
5. Utilize Air Bleeding Procedures: The 2021 Subaru Outback, like many modern vehicles, can be prone to air pockets.
   • Filler Neck: Continue to fill the coolant. Squeeze the upper and lower radiator hoses repeatedly to help dislodge air bubbles. You may see bubbles rise to the filler neck.
   • Heater Core Bleed: Run the engine with the heater on full blast and the fan on low while the radiator cap is off. This helps to circulate coolant through the heater core and expel air.
   • Raise Front of Vehicle: Elevating the front of the vehicle can sometimes help move trapped air towards the radiator filler neck.
6. Run Engine & Monitor: Start the engine and let it warm up to operating temperature with the radiator cap off (or loosely placed if coolant is overflowing). As the thermostat opens, the coolant level may drop; add more coolant as needed. Watch for air bubbles escaping. The electric cooling fans should cycle on and off.
7. Squeeze Hoses: With the engine running, continue to gently squeeze the upper and lower radiator hoses to release trapped air.
8. Reservoir: Fill the coolant reservoir to the "FULL" mark.
9. Final Check: Once no more bubbles appear and the coolant level stabilizes, install the radiator cap securely. Drive the vehicle and recheck the coolant level in the reservoir after the engine has cooled down. Top off as necessary.

Common Cooling System Issues for this Generation

The 2021 Subaru Outback is part of the sixth generation (BT series) and generally has a robust cooling system. However, like any vehicle, some common issues can arise:

• Head Gasket Leaks (less common in newer generations): While significantly improved from earlier generations, head gasket issues were historically a weakness for Subaru. The FB and FA series engines found in the 2021 Outback are much more reliable in this regard, but it's still something to be aware of, especially if neglected coolant maintenance leads to overheating.
• Radiator Leaks: Radiators can develop leaks over time due to corrosion, impact from road debris, or fatigue of plastic end tanks. Keep an eye out for pinkish or bluish stains under the vehicle.
• Hose Leaks: Rubber hoses can degrade, crack, and leak over time due to age and exposure to heat and pressure. Inspect hoses for swelling, cracking, or softness.
• Water Pump Failure: The water pump circulates coolant. Bearings can wear out, leading to leaks from the weep hole or a grinding noise. This is typically a longer-term wear item.
• Thermostat Issues: A faulty thermostat can cause the engine to overheat (stuck closed) or run too cool (stuck open). Symptoms include fluctuating temperature gauges or slow engine warm-up.
• Coolant Expansion Tank Cracks: The plastic coolant expansion tank can develop cracks due to heat cycles and age, leading to slow coolant leaks.

Regular inspection of your coolant level, color, and hoses can help catch these issues early. Using the correct Subaru Super Coolant and adhering to the recommended maintenance schedule is paramount for the longevity of your cooling system.

Find a trusted shop on Repairius.