2015 Subaru Outback Coolant Capacity & Type

The 2015 Subaru Outback typically holds around 7.9 to 8.6 quarts (7.5 to 8.1 liters) of coolant in its cooling system, depending on the engine. This guide will provide detailed information on coolant capacity, type, maintenance, and common issues for your 2015 Outback.

Quick Answer

• Total Cooling System Capacity: 7.9 - 8.6 quarts (7.5 - 8.1 liters)
• OEM Coolant Spec: Subaru Super Long Life Coolant (SLLC) - Blue, Phosphate Hybrid Organic Acid Technology (P-HOAT)
• Mix Ratio: 50/50 pre-mixed or concentrate mixed with distilled water

Capacity by Engine Option

Flush Interval

• Normal Duty: Subaru recommends an initial coolant flush at 137,500 miles or 11 years, whichever comes first. Subsequent flushes are recommended every 75,000 miles or 6 years.
• Severe Duty: If your driving conditions are considered severe (e.g., frequent towing, extreme temperatures, dusty conditions), it's advisable to inspect your coolant more frequently and consider reducing the flush interval to around 60,000 miles or 5 years.

How to Refill & Bleed

Refilling and bleeding the cooling system on a 2015 Subaru Outback is crucial to prevent air pockets, which can lead to overheating. Always perform this on a cool engine.

1. Drain: Locate the drain plug on the bottom of the radiator and open it to drain the old coolant into a suitable container. There may also be drain plugs on the engine block; consult your service manual for their locations.
2. Flush (Optional): If performing a full flush, close the drain plugs and fill the system with distilled water. Run the engine with the heater on high until it reaches operating temperature, then drain. Repeat until the drained water is clear.
3. Refill: Close all drain plugs. Slowly fill the radiator with the specified Subaru Super Long Life Coolant (SLLC) 50/50 mix. Fill the reservoir to the "FULL" mark.
4. Bleed Air: Start the engine with the radiator cap off (or funnel in place). Turn the heater to full hot and fan on low. Allow the engine to warm up to operating temperature. As the thermostat opens, the coolant level in the radiator may drop; continue to top off as needed. Squeeze the upper and lower radiator hoses to help dislodge air bubbles. Look for small air bubbles escaping from the radiator filler neck. Some Subaru models, including the Outback, are known to be sensitive to air pockets, so take your time with this step. Subaru often includes a small air bleed valve or radiator cap design to aid in bleeding. Ensure your overflow reservoir is filled to the "full" line.
5. Test Drive & Recheck: Once no more bubbles appear, install the radiator cap. Take the car for a short drive, monitoring the temperature gauge. After the engine has cooled completely, recheck the coolant level in the overflow reservoir and top off if necessary.

Common Cooling System Issues for this Generation

Owners of the 2015 Subaru Outback (and the fifth generation, 2015-2019) may encounter a few common cooling system issues:

• Head Gasket Leaks: While less prevalent than in earlier generations, some 2.5L FB25 engines can still develop external head gasket leaks, often manifesting as minor coolant seepage. Internal leaks are rarer but can lead to overheating or coolant consumption.
• Radiator Leaks: Over time, the plastic end tanks of the radiator can become brittle and crack, leading to coolant leaks. Watch out for pink or blue residue around the radiator, especially near the end tanks.
• Thermostat Failure: A failing thermostat can cause the engine to overheat (if stuck closed) or run cooler than optimal (if stuck open). Symptoms include fluctuating temperature gauges or slow warm-up times.
• Water Pump Leaks: The water pump can eventually develop leaks, signaled by coolant drips underneath the front of the vehicle or a whining noise from the accessory belt area. Proactive replacement around 100,000 miles is often recommended.
• Coolant Expansion Tank Cracks: The plastic coolant expansion tank can crack due to heat cycling and age, leading to slow coolant loss.

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