Can I use any coolant in my Subaru Forester?
No. Subaru Foresters require coolant that meets Subaru’s specification and is compatible with aluminum engine components. Use Subaru Genuine Long Life Coolant or an approved equivalent that is ethylene glycol‑based and silicate‑free. Mixing different coolant types can lead to corrosion, deposits, and cooling system failures.
What your Forester coolant needs are
Subaru’s guidance centers on using an ethylene glycol–based coolant that is specifically formulated to be safe for aluminum engines and to provide long‑life protection. The coolant may be sold as a concentrated or pre‑mixed (50/50) product, but the key requirement is that it carries Subaru’s approval or explicitly meets Subaru’s cooling system specifications. The bottom line is to avoid coolants that are not tested or labeled as compatible with Subaru engines.
Which coolants are acceptable
Consider the following options only if they clearly meet Subaru’s specification for your Forester. Always verify the product label or service literature confirms compatibility with Subaru engines.
- Subaru Genuine Long Life Coolant (pre‑diluted 50/50) or Subaru Genuine Concentrate prepared according to the label.
- Other brands that explicitly state compatibility with Subaru engines and are ethylene glycol–based, low in silicates, and suitable for aluminum components (look for a Subaru approval or equivalent specification on the bottle).
- Coolants marketed as compatible with “HOAT” or “OAT” systems and specifically noted as safe for aluminum engines and Subaru vehicles.
Do not assume all “universal” or green/orange automotive coolants are appropriate. Avoid coolants that contain silicates or additives not approved by Subaru, and never mix incompatible coolant chemistries. Always check the product label and your owner’s manual before purchasing.
Practical guidelines for topping up or changing coolant
When you top up or perform a full coolant change, follow these steps to ensure proper protection and longevity of the cooling system.
- Consult your owner’s manual to confirm the correct coolant type and dilution (many Foresters use a 50/50 mix of distilled water and coolant).
- Purchase Subaru Genuine Long Life Coolant or an approved equivalent that explicitly meets Subaru’s specifications and is ethylene glycol–based and silicate-free.
- If using a concentrate, mix it only with distilled water as directed on the product label to achieve the recommended 50/50 ratio.
- Drain the cooling system completely if you are doing a full change, flush if needed, and refill with the correct mixture. Do not use tap water unless the manual specifies it is acceptable.
- After refilling, run the engine to operating temperature with the heater on to bleed air, then check for leaks and recheck the level when the system is cold.
Following these steps helps protect the engine from corrosion and overheating and ensures your Forester’s cooling system operates as designed.
Common mistakes to avoid
These points cover frequent missteps that can compromise cooling system reliability.
- Using a coolant that isn’t labeled compatible with Subaru engines or that isn’t ethylene glycol–based.
- Mixing coolant types or mixing a concentrate with a non‑compatible concentrate without confirming compatibility.
- Assuming all “green” or universal coolants are safe for Subaru engines without checking the specification.
- Ignoring dilution recommendations or failing to bleed air after a fill, which can cause overheating or air pockets.
Sticking to Subaru‑approved coolant and the recommended procedures helps minimize risk and extend the life of your cooling system.
Summary
For a Subaru Forester, you should not use just any coolant. Use only Subaru‑approved coolant—typically Subaru Genuine Long Life Coolant or an equivalent that is ethylene glycol–based, silicate‑free, and compatible with aluminum engines. Always follow the owner’s manual, avoid mixing different coolant chemistries, and perform proper bleeding after a refill. By sticking to approved coolants and proper procedures, you help ensure reliable cooling performance and engine longevity.
