Understanding the correct 2018 Subaru Forester coolant type is essential for preserving the longevity and efficiency of your vehicle’s engine. This specific model year utilizes a sophisticated horizontally-opposed engine that generates significant heat, requiring a precise coolant formulation to manage thermal cycles effectively. Using the wrong mixture can lead to corrosion, overheating, and potentially severe mechanical failure, making this a critical maintenance item for any owner.
Factory Specifications and OEM Requirements
For the 2018 model year, Subaru mandates the use of Subaru Blue Coolant Type S or an equivalent Silicated Organic Additive Technology (Si-OAT) formulation. The factory fill is typically a 50/50 dilution of the concentrated coolant with deionized water to achieve the proper freeze point and boiling characteristics. This specific chemistry is engineered to protect the aluminum components and the magnesium alloy found in the water pump, which are standard in the FB20 engine utilized in this model year.
Identifying the Correct Coolant Color
Visual identification is the quickest method to verify you have the right product. The Subaru Blue Coolant Type S is distinguished by its vibrant blue dye. This color is not merely aesthetic; it indicates the specific additive package required for the Subaru brand. You should never rely solely on color, but it is a primary indicator when selecting a product on the shelf. If you are performing a system flush, the old fluid will likely be a greenish or rusty color, signaling the need for replacement.
The Risks of Incorrect Coolant Mixtures
Deviating from the recommended coolant type can have immediate and long-term consequences. Incompatible coolants, such as traditional green silicate-based formulas, can react negatively with the Si-OAT chemistry, resulting in gel-like deposits that clog radiator passages and heater cores. Furthermore, using water alone or tap water introduces minerals that cause scale buildup and significantly reduce the efficiency of heat transfer, leading to increased engine temperatures and reduced fuel economy.
Maintenance Schedule and Fluid Replacement
While the 2018 Forester is known for reliability, adhering to the maintenance schedule is crucial for cooling system integrity. Subaru typically recommends a coolant flush and replacement approximately every 100,000 miles or 10 years, whichever comes first. However, inspecting the coolant level and condition during regular oil changes is a good practice. Look for signs of contamination, such as oiliness (which indicates a head gasket leak) or visible rust, which suggests the protective additives have degraded.
DIY vs. Professional Service
Homeowners can perform a coolant top-off or complete flush, but it requires careful preparation. You must ensure the engine is completely cool before opening the radiator cap to avoid being scalded by pressurized steam. When performing a refill, it is vital to burp the system properly to remove air pockets. For those uncomfortable with this process, a professional technician can verify the specific gravity of the mixture and ensure the system is free of leaks.
Performance and Environmental Considerations
The correct coolant type does more than just prevent overheating; it contributes to the overall performance of the 2018 Forester. The superior heat transfer properties of the Si-OAT formula allow the engine to run within the optimal temperature window, improving efficiency and reducing cold-start emissions. Additionally, many modern Subaru coolants are designed with environmental safety in mind, utilizing less toxic components compared to the older ethylene glycol-based formulas of the past.
Where to Purchase the Right Product
When sourcing coolant for your 2018 Forester, prioritize products that explicitly state compatibility with Subaru vehicles or Japanese Domestic Market (JDM) specifications. Major auto parts chains often carry Subaru Blue Coolant Type S in gallon containers. Alternatively, you can purchase pre-diluted 50/50 mixtures that are ready to use, eliminating the guesswork associated with mixing concentrate. Always check the expiration date on the container, as the additives can settle and degrade over time.
