What are the ingredients in Subaru coolant?
Subaru coolant is an ethylene glycol–based antifreeze mixed with water and a corrosion-inhibitor package; the exact additives depend on the specific Subaru product you’re using (such as Subaru Genuine Long Life Coolant vs. conventional coolant). The label on the bottle or the owner's manual will specify the precise components and their concentrations.
Subaru coolant formulations: SLLC vs Conventional
Two main Subaru coolant lines are commonly discussed for modern vehicles: Subaru Genuine Long Life Coolant (SLLC) and Subaru Conventional Coolant. The following outlines the typical ingredients in these formulations, noting that exact chemical details are proprietary for some products.
Subaru Genuine Long Life Coolant (SLLC)
The SLLC formulation is designed for extended service intervals and strong protection of Subaru engines. The exact chemical composition is proprietary, but the coolant generally consists of a glycol base, water, a corrosion-inhibitor package tailored for Subaru cooling systems, and a colorant to distinguish the product.
- Ethylene glycol — base antifreeze agent
- Water — usually demineralized or distilled water
- Proprietary corrosion inhibitors — a package designed to protect metal components in Subaru engines
- Dye/colorant — added for product identification
When using SLLC, follow Subaru’s guidance for preparation, mixing ratios (often 50/50 with water, depending on climate), and service intervals. Do not substitute with non-SLLC products unless a compatible specification is confirmed.
Subaru Conventional Coolant
Subaru’s conventional coolant products use a more traditional inhibitor package and are often formulated to meet regional standards. The exact additives are not always disclosed publicly, but you can expect a glycol base with water, an inorganic or mixed corrosion-inhibitor system, and a dye for identification.
- Ethylene glycol — base antifreeze agent
- Water — usually demineralized or distilled water
- Corrosion inhibitors — inorganic additives (and/or traditional inhibitor packages) to protect cooling system metals
- Dye/colorant — added for product identification
As with SLLC, always verify compatibility with your vehicle and follow the manufacturer’s recommended replacement intervals and dilution guidelines.
What to know about ingredients and compatibility
Understanding what’s in Subaru coolant helps ensure proper maintenance and prevent damage from using the wrong product. Since Subaru sometimes changes formulations or updates recommended products by model year, rely on the exact product label or Subaru’s official guidance for your vehicle. Mixing different coolant types can reduce protection and may require a system flush to avoid deposits or corrosion.
Practical guidance for Subaru owners
If you’re replacing coolant or topping up, follow these steps to avoid issues:
- Use Subaru Genuine Coolant or a product that explicitly meets Subaru’s specification for your model/year.
- Do not mix SLLC and conventional coolants unless the manufacturer confirms compatibility.
- Follow the recommended dilution ratio (often 50/50 with water) and consider climate and driving conditions.
- Flush the cooling system if you’re changing the formulation or if you’re unsure about the previous coolant type.
For exact ingredients and compatibility details, consult your owner’s manual, the Subaru customer service line, or a Subaru-authorized service center.
Summary
Subaru coolant is based on ethylene glycol with water and a corrosion-inhibitor package, but the exact additives vary by product (SLLC vs. conventional). The key elements you’ll see listed on labels are the glycol base, water, corrosion inhibitors, and dye. Always use the specified Subaru coolant for your vehicle, and follow proper mixing, flushing, and service interval guidelines to maintain cooling-system protection.
