Understanding the 2018 Subaru Forester coolant type is essential for maintaining the longevity and performance of your all-weather vehicle. This specific model year utilizes a specialized long-life coolant, often referred to as Subaru Blue, which is a hybrid organic acid technology (HOAT) formulation. Using the correct fluid is not merely a recommendation; it is a critical factor in preventing corrosion within the aluminum engine blocks and ensuring the radiator operates efficiently under varying temperature conditions.
The Specifics of Subaru Coolant
The 2018 Forester requires a specific chemical composition that differs significantly from traditional green silicate coolants. Subaru mandates the use of a blue-colored coolant that meets the Subaru Global Specification. This specification is designed to protect the complex aluminum components found in the horizontally-opposed "Boxer" engine and the continuously variable transmission (CVT). The HOAT formula provides a balance between protecting aluminum radiators and preventing the scaling that can occur with hard water, making it suitable for the diverse climates where the Forester is driven.
Identifying the Correct Product
When purchasing coolant for your 2018 model, you should look for labels that explicitly state "Subaru Blue" or "Subaru HOAT Coolant." You will often find products pre-diluted in ready-to-use bottles, or you may find the concentrate form. If you buy the concentrate, it is almost always mixed with distilled water at a 50/50 ratio. Avoid using universal or generic coolants that are bright green or orange, as these can react negatively with the Subaru's cooling system seals and hoses, potentially leading to leaks and premature failure.
Why the Coolant Type Matters
The cooling system in the 2018 Forester is pressurized and operates at high temperatures. The coolant serves three vital roles: heat transfer, freeze protection, and corrosion inhibition. The Subaru Blue formula is engineered to remain stable over a long period, which is why Subaru typically recommends a coolant flush only every 100,000 miles. Using an incorrect type of coolant can lower the boiling point, cause acid buildup, and lead to the erosion of the water pump or heater core, resulting in expensive repairs down the line.
Maintenance and Inspection
During routine maintenance, technicians should check the coolant's pH level to ensure it remains within the alkaline range. The 2018 Forester's coolant should maintain a blue color; if it turns rusty or brown, this indicates that the anti-corrosion additives are depleted. Driving with depleted coolant can cause overheating and severe engine damage. When topping off the reservoir between services, always use a 50/50 mix of the Subaru-spec coolant and distilled water to maintain the proper chemical balance.
Common Mistakes to Avoid
Do not mix different colors of coolant, as this creates a gel-like substance that blocks the radiator.
Avoid topping off with straight coolant, as this disrupts the carefully balanced additive package.
Never use water alone, even in an emergency, as it lacks the necessary inhibitors and will corrode the system.
Do not flush the system with vinegar or other home remedies, as these can damage aluminum components.
OEM vs. Aftermarket Options
While Subaru dealers offer the genuine Subaru Blue coolant, many reputable aftermarket brands produce fluids that meet the Subaru Global Specification. When choosing an aftermarket brand, ensure the product explicitly states compatibility with 2018 Subaru Foresters and meets the required HOAT standard. While the OEM fluid is the guaranteed match, a high-quality aftermarket alternative can be a cost-effective solution as long as it adheres to the technical specifications required for the Boxer engine.
