The 2018 Subaru Legacy equipped with the 2.5L 4-cylinder FB25 engine requires specific attention to lubrication to ensure reliable performance and longevity. Because Subaru vehicles operate with precision-engineered internal components, using the correct oil grade and filtration system is essential for maintaining engine health. This engine specifically requires a 0W-20 viscosity synthetic motor oil, and the fluid capacity is 5.1 quarts when the oil filter is also replaced. Adhering to these specifications helps prevent premature wear and maintains the efficiency of the vehicle’s continuously variable transmission and all-wheel-drive system.
Recommended AMSOIL Products
- AMSOIL Signature Series 0W-20 100% Synthetic Motor Oil – The ultimate protection for your Legacy, offering up to 25,000 miles of service intervals and 75% more engine protection against horsepower loss and wear compared to industry standards.
- AMSOIL Extended-Life 0W-20 100% Synthetic Motor Oil – Ideal for drivers seeking extended drain intervals of up to 20,000 miles, featuring superior cleaning power to help keep the engine running smoother and longer.
- AMSOIL OE 0W-20 100% Synthetic Motor Oil – A cost-effective full synthetic option that fights sludge and deposits while providing reliable protection comparable to original equipment standards.
- AMSOIL 0W-20 100% Synthetic High-Mileage Motor Oil – Specifically formulated for vehicles with over 75,000 miles, featuring a boosted detergent package and additives designed to reduce sludge by 67%.
- AMSOIL Oil Filter – Provides 99% filtering efficiency at 20 microns, offering greater capacity for contaminants and lower restriction to keep critical engine parts properly lubricated.
- WIX Oil Filter – Features premium media that offers improvements over original equipment manufacturer branded filters, ensuring reliable filtration for your oil change.
- WIX Air Filter – Provides clean airflow to the engine with premium media that outperforms standard OEM-branded filters, helping maintain fuel economy and engine performance.
- AMSOIL Passenger Car & Light Truck Antifreeze & Coolant – A unique poly-organic acid formulation that exceeds OEM requirements, offering protection up to 150,000 miles or 5 years with a 50/50 pre-mix for immediate use.
- AMSOIL Propylene Glycol Antifreeze and Engine Coolant – A concentrated option that provides superior corrosion and erosion protection, lasting up to 150,000 miles or 5 years in passenger cars when mixed with distilled water.
- AMSOIL 100% Synthetic CVT Fluid – Delivers exceptional metal-to-metal frictional properties essential for the Subaru transmission, ensuring smooth operation even in severe driving conditions.
- AMSOIL DOT 3 and DOT 4 100% Synthetic Brake Fluid – Offers excellent ABS and traction-control responsiveness with stable viscosity over a wide temperature range for enhanced braking safety.
Selecting the right lubricant for your 2018 Subaru Legacy is not just about meeting the manufacturer’s baseline requirements; it is about providing protection that exceeds the stresses of daily driving. The FB25 engine, while reliable, benefits significantly from the advanced additive packages found in AMSOIL Signature Series 0W-20 or AMSOIL Extended-Life 0W-20 motor oils. These oils are engineered to resist breakdown under high heat and provide superior flow at low temperatures, ensuring that critical engine components are lubricated immediately upon startup. The oil capacity of 5.1 quarts, when including a filter change, is a key metric for maintaining the correct oil pressure and volume required for the engine’s variable valve timing and other sensitive systems.
Transmission and Drivetrain Protection
The 2018 Legacy’s transmission system requires specialized attention to ensure smooth power delivery. For models equipped with the TR580 automatic transmission, the fluid capacity for a total fill is 11.9 quarts. Using the correct fluid is vital for the longevity of the transmission and the torque converter. AMSOIL 100% Synthetic CVT Fluid is designed to provide exceptional frictional properties that prevent shudder and ensure precise shifting. This fluid offers protection that helps the transmission withstand the high stress of Subaru’s all-wheel-drive system, reducing wear on internal gears and clutches.
Engine Air Filtration and Cooling Systems
Proper filtration is just as important as the oil itself. A clogged air filter forces the engine to work harder, reducing fuel efficiency and power. The WIX Air Filter recommended for this vehicle offers premium media that effectively traps dust and debris while allowing optimal airflow. This helps the engine breathe efficiently, which is crucial for the FB25 engine’s performance. Furthermore, the cooling system plays a vital role in engine health. The coolant capacity for the 2018 Subaru Legacy is 8.2 quarts. Maintaining the correct mixture prevents overheating in summer and freezing in winter. AMSOIL Propylene Glycol Antifreeze and Engine Coolant is a concentrated option that greatly surpasses standards for metallic corrosion and erosion protection. Alternatively, the ready-to-use AMSOIL Passenger Car & Light Truck Antifreeze & Coolant offers the convenience of a 50/50 pre-mix formulation that protects all cooling system metals, gaskets, and hoses.
Brake Systems and Fuel Care
While often overlooked, brake fluid is critical for safety. The 2018 Subaru Legacy utilizes hydraulic brake fluid that should be DOT 3 compatible. Over time, brake fluid absorbs moisture from the air, which lowers its boiling point and can lead to brake fade under heavy use. AMSOIL DOT 3 and DOT 4 100% Synthetic Brake Fluid provides a stable viscosity over a wide temperature range and offers excellent ABS responsiveness. For those looking to improve fuel economy and power, AMSOIL P.i. Performance Improver Gasoline Additive is a highly effective solution. This additive restores up to 14% horsepower and clears carbon deposits from direct injection injectors, helping to maintain the engine’s peak performance.
Winterization and Storage
For owners in colder climates or those who engage in seasonal storage, specific products are available to protect the vehicle. AMSOIL Engine Fogging Oil is designed to protect internal engine components during storage, preventing rust and corrosion on pistons and cylinder walls. Additionally, for the winter season, AMSOIL Gasoline Stabilizer helps keep fuel fresh for up to 12 months, preventing varnish and gum buildup that can clog fuel systems.
About the Vehicle
The 2018 Subaru Legacy is a mid-size sedan that has established a strong reputation for reliability and safety over its many generations. Built on Subaru’s platform, this model is powered by the flat-four “Boxer” engine, a design feature that places the engine components low in the chassis. This layout lowers the vehicle’s center of gravity, which significantly enhances handling and stability, especially during cornering or in adverse weather conditions. The 2.5L 4-cylinder FB25 engine delivers a balance of fuel efficiency and adequate power for daily commuting and highway driving.
Subaru’s all-wheel-drive system is a hallmark of the brand, offering superior traction in snow, rain, and on rough roads. This makes the Legacy a favorite among drivers in regions with harsh winters or those who frequently travel on unpaved or wet surfaces. The interior is typically spacious, offering comfort for both front and rear passengers, while the trunk provides ample storage space, making it a versatile choice for families or individuals who need a practical vehicle. The 2018 model year continued the Legacy’s legacy of high safety ratings, often receiving top marks in crash tests and featuring advanced driver-assist technologies that were becoming standard in the class.
Despite its robust design, the 2018 Legacy, like any vehicle, faces common wear and tear issues that can be mitigated with high-quality lubricants. One common issue for Subaru Boxer engines is carbon buildup on the intake valves, particularly in direct injection applications, which can affect engine smoothness and efficiency. The use of fuel additives like AMSOIL P.i. Performance Improver can help mitigate this by keeping injectors and valves clean. Another potential issue is oil consumption, which can occur in older engines or those subjected to severe driving conditions. AMSOIL 0W-20 100% Synthetic High-Mileage Motor Oil formulations contain seal conditioners that help reduce oil consumption and prevent leaks, extending the life of the engine. Additionally, the CVT transmission can sometimes experience shudder or hesitation due to fluid degradation; using a premium synthetic AMSOIL 100% Synthetic CVT Fluid can prevent these friction-related issues and ensure smooth shifting. Finally, coolant leaks from aging hoses and radiators are common in higher-mileage vehicles, but using a high-quality antifreeze with corrosion inhibitors like AMSOIL Propylene Glycol Antifreeze and Engine Coolant can help protect the cooling system components and prevent leaks, ensuring the engine stays at the optimal operating temperature.