The Mercury 25W-50 Synthetic Blend 3.78L Oil is a high-performance marine engine oil specifically developed for demanding four-stroke marine applications. Whether you operate a high-horsepower outboard, sterndrive, or inboard engine, this oil is built to deliver exceptional protection and reliability in harsh saltwater and freshwater conditions.
Built for Heavy-Duty Marine Use
Marine engines face extreme loads, long hours, and variable RPM. That’s why Mercury designed this synthetic blend to offer enhanced film strength and superior thermal stability. The Mercury 25W-50 Synthetic Blend 3.78L Oil maintains optimal viscosity in high-heat environments, which is critical for preventing engine wear during prolonged use at high speeds or under heavy loads.
Corrosion and Moisture Protection
Saltwater can be brutal on internal components. This oil features advanced anti-corrosion additives that create a barrier against moisture, oxidation, and rust. Even during storage or in humid climates, your engine stays protected. This helps reduce long-term maintenance and keeps your motor running strong.
Clean Operation for Extended Engine Life
This oil helps minimise carbon buildup and internal sludge, ensuring cleaner pistons, valves, and crankcase surfaces. Cleaner internals lead to better combustion, improved fuel economy, and reduced exhaust emissions. As a result, your engine starts more easily, idles more smoothly, and operates more efficiently overall.
Perfect for Big-Block Four-Strokes
This synthetic blend is particularly well-suited for high-displacement four-stroke marine engines that generate more heat and pressure. It’s ideal for use in applications such as offshore fishing, water sports, or commercial marine work, where consistent performance and durability are non-negotiable.
Reliable in Extreme Conditions
The oil’s resistance to shear and breakdown makes it an excellent choice for boats that operate in extreme heat or under long, continuous loads. Its robust formula provides dependable performance during high-speed operation, towing, and extended running hours.
Convenient 3.78L Size
The 3.78-litre bottle gives you enough oil for full changes or several top-ups, depending on your engine’s capacity. It’s a great size for regular maintenance and ensures you’re never left short when it’s time to service your boat.