Do subarus require special coolant?
Yes. Subarus generally require a coolant that meets Subaru's own specification—Subaru Genuine Long Life Coolant (SLLC) or an equivalent HOAT coolant that is phosphate- and silicate-free. Use the recommended 50/50 mix with distilled water, unless a pre-mixed version is supplied by Subaru or the coolant manufacturer. Do not rely on generic or universal coolants unless they explicitly state compatibility with Subaru engines.
What makes Subaru coolant special
Subaru designs its cooling system for aluminum engine components and a specific network of radiators and heater cores. To protect these materials over the long term, Subaru recommends a coolant that is phosphate-free, silicate-free, and ethylene glycol-based, formulated to meet Subaru’s own specification. The official coolant is marketed as Subaru Genuine Long Life Coolant or an equivalent coolant tested to Subaru’s standards. Compatibility with other brands is not always guaranteed, and using an off-spec coolant can reduce corrosion protection or lead to leaks and performance issues.
Which coolants are appropriate and which to avoid
The safest choice is to use Subaru Genuine Long Life Coolant (SLLC) or a coolant that explicitly states it meets Subaru's specification. You should avoid:
- Generic "green" or "universal" coolants that do not specify compatibility with Subaru engines
- Coolants that are not phosphate- and silicate-free or not HOAT-type if Subaru requires HOAT
- Mixing different coolant types or brands unless directed by Subaru
- Using straight water in place of coolant (which can compromise protection)
When in doubt, consult the owner’s manual or contact a Subaru dealer or trusted mechanic to confirm the correct coolant for your model and year.
How to replace and maintain your coolant
Replacing coolant on a Subaru involves draining the old fluid, flushing the system if needed, and refilling with the correct mix. The steps below outline a general process; always follow the model-specific service procedure from Subaru for your year and engine type.
Before you begin, this paragraph explains what the upcoming steps cover: selecting the right coolant, preparing the vehicle, draining and flushing, refilling with the proper mix, bleeding air from the system, and verifying level and leaks.
- Check the owner's manual for the exact coolant specification and the recommended mix (often 50/50 with distilled water, or a pre-mixed version). Use Subaru Genuine Long Life Coolant or an equivalent that meets Subaru’s spec.
- Prepare your tools and workspace. Use distilled water for any dilution, have a clean drain pan, funnel, and rags ready; ensure the engine is cool before starting.
- Drain the old coolant: place a pan under the drain, open the radiator drain plug and any heater-core drains, and allow the fluid to flow out completely.
- Flush (optional but recommended if you’re replacing old coolant or addressing contamination). Use a cooling-system flush product or a thorough water rinse until the drained fluid runs clear.
- Refill with the correct coolant: pour in the prepared 50/50 mix or pre-mixed coolant to the proper level. Monitor the expansion tank level as you fill.
- Bleed air from the system: some Subarus require venting the cooling system to remove air pockets. Run the engine with the heater on and follow the service manual’s bleeding procedure until the temperature stabilizes and the level settles.
- Check for leaks and confirm readings: after reaching normal operating temperature, inspect hoses, the radiator, and the water pump for leaks; recheck the expansion tank level and top up if needed.
- Dispose of old coolant responsibly: used coolant is hazardous and should be taken to an authorized recycle facility or automotive shop that handles hazardous waste.
Regularly maintaining the correct coolant type and level helps protect the engine’s aluminum components, prevents rust, and maintains proper freeze and boil-over protection across seasons.
Common questions
Do older Subarus require different coolant?
Most Subarus built from the early 2000s onward use the same general guidance: use a coolant that meets Subaru’s specification. However, there can be model- or region-specific variations, so always check the owner’s manual or consult a Subaru dealer for your exact year and engine.
Can I mix coolant brands?
Mixing is not recommended unless the brands explicitly state compatibility with Subaru engines. If you’re unsure, drain and flush the system before refilling with the correct coolant.
Summary
Subarus generally require a coolant that meets Subaru's own specification—Subaru Genuine Long Life Coolant or an equivalent HOAT-type coolant that is phosphate- and silicate-free. Using off-spec coolants or mixing incompatible types can compromise cooling system protection and lead to corrosion, leaks, or overheating. Always verify the correct coolant for your specific model and year via the owner’s manual or a Subaru service professional, and follow the recommended service intervals for flushing and replacement. Proper coolant selection and maintenance help keep your Subaru running reliably in all seasons.
