The 2015 Subaru Impreza uses a premixed ethylene glycol-based long-life coolant designed specifically for Subaru engines. Use a 50/50 mix with distilled water, and choose a coolant that is silicate-free and meets Subaru’s specifications for aluminum engines. Avoid coolants not labeled for Subaru use or those with incompatible additives.
What to use and what to avoid
Subaru specifies a coolant that protects aluminum engine components and prevents corrosion. The safest option is Subaru Genuine Long Life Coolant, but a premium HOAT or OAT coolant that explicitly meets Subaru’s compatibility and is labeled as suitable for Subaru engines can also be used.
Subaru coolant specifications explained
Key attributes to look for: silicate-free formulation, corrosion inhibitors appropriate for aluminum engines, and a specification that indicates compatibility with Subaru vehicles. Always follow the manual or dealer guidance when selecting a coolant.
- Subaru Genuine Long Life Coolant (premixed 50/50) for most Impreza models
- Premium HOAT or OAT coolant that explicitly states compatibility with Subaru engines and meets Subaru’s specification (silicate-free)
- Avoid coolants not labeled for Subaru use or that contain silicates or additives incompatible with aluminum engines
Using the correct coolant helps prevent corrosion and overheating and reduces the risk of cooling-system problems.
How to replace or top off the coolant
The following steps are a general guide. Always refer to the owner’s manual or a certified mechanic for your vehicle’s exact procedure and capacity.
- Ensure the engine is cool and remove the radiator cap only after the system depressurizes.
- Place a drain pan under the radiator drain valve and open it to remove the old coolant. Collect for proper disposal.
- Close the drain and locate the coolant reservoir. Refill with Subaru Genuine Long Life Coolant or an approved HOAT/OAT coolant in a 50/50 premixed ratio if your product is premixed.
- Bleed the cooling system to remove air according to the service manual, running the engine with the heater on and topping off as needed until the level stabilizes.
- Check for leaks, reinstall the cap, and recheck the level once the system has cooled.
Properly bleeding and filling the cooling system helps ensure consistent operation and prevents air pockets that can cause hot spots.
Additional notes and best practices
Always verify the exact coolant type listed in your owner’s manual. If in doubt, contact a Subaru dealer or a qualified mechanic. Use distilled water if you are mixing your own 50/50 solution, and do not mix different coolant types unless the manufacturer confirms compatibility.
Summary
For a 2015 Subaru Impreza, use a premixed, ethylene glycol-based long-life coolant that is silicate-free and meets Subaru specifications—typically Subaru Genuine Long Life Coolant (50/50). If you opt for a third-party coolant, ensure it explicitly states compatibility with Subaru engines and uses HOAT or OAT technology. Always follow proper mixing, bleeding, and disposal procedures to protect the cooling system and engine.