Parts for your 2015 Subaru Forester-Coolant

2015 Subaru Forester coolant — what it does and how to look after it

Coolant is absolutely relevant to the 2015 Subaru Forester. Subaru’s own technical literature — including the 2015 Forester Owner’s Manual and Subaru Service & Technical Information — specifies a liquid-cooled system using Subaru Genuine Super Coolant (blue, long-life). Both the FB25 (2.5‑litre) and FA20F (2.0XT turbo) engines are designed around this coolant to manage heat, prevent corrosion and keep the heater working properly. Subaru’s maintenance schedule notes an extended first replacement interval with its Super Coolant.

In this Forester, coolant does much more than stop freezing. It carries heat away from the engine to the radiator, resists boil‑over on scorching summer days, protects alloy components from corrosion and scale, and helps lubricate the water pump. Subaru’s blue Super Coolant is a phosphate‑OAT formulation, premixed to around 50/50, which hits the sweet spot for protection and heat transfer. It’s the right colour, chemistry and life for the job.

For servicing, the advice is straightforward: check the overflow bottle under the bonnet when the engine is cold and keep the level between the marks. Top up only with Subaru Super Coolant (blue) to avoid mixing chemistries. If it needs frequent top‑ups, that’s a sign to get the system pressure‑tested — could be a weep at a hose, radiator, water pump or cap.

Replacement timing is generous thanks to the long‑life formula: the factory schedule calls for the first change at up to 11 years/220,000 km, then typically every 6 years/120,000 km thereafter. If any cooling component is replaced, or the coolant looks contaminated, replace sooner. When changing coolant, use a spill‑free funnel or a vacuum fill tool to purge air, set the cabin heater to hot, and run the engine until the fans cycle so the thermostat opens and air can bleed out. Always dispose of old coolant responsibly — it’s toxic to pets and wildlife.

• Never open the radiator cap hot — wait until fully cool.
• Inspect hoses, clamps and the radiator cap during each service.
• Stick with the correct Subaru blue P‑OAT coolant, don’t mix with green “universal” types.
• If the temp gauge creeps up, or there’s a sweet smell or white crust around fittings, book a check straight away.

Popular questions about 2015 Subaru Forester coolant

What coolant type should be used?
Subaru specifies Subaru Genuine Super Coolant (blue), a phosphate‑OAT, silicate‑ and borate‑free long‑life premix. It’s designed for Subaru alloy engines and seals, and mixing it with generic green coolant isn’t recommended.

If you’re topping up, match the blue long‑life coolant. If a full change is due, use the same chemistry to maintain corrosion protection and proper service intervals.

When should the coolant be changed?
With Subaru Super Coolant, the first change can be up to 11 years/220,000 km, then typically every 6 years/120,000 km. Harsh use, component replacement, or any signs of contamination justify changing sooner.

Follow the time as well as kilometres — even low‑km cars benefit from a periodic refresh to renew inhibitors.

How do you check and top up the coolant safely?
When the engine is cold, check the translucent overflow bottle and top up to the “FULL” mark with Subaru blue Super Coolant. Avoid opening the radiator cap unless necessary and never when hot.

If the level keeps dropping, have a technician inspect for leaks or internal issues before it turns into an overheating drama.