Marine engines operate under high loads and RPMs for extended periods of time, causing traditional automotive oils to break down and lose viscosity. To ensure good protection, the NMMA set minimum shear stability requirements for FC-W. AMSOIL Formula 4-Stroke® Marine Synthetic Motor Oil greatly exceeds the FC-W shear stability requirements, outperforming competitive oils to deliver a superior lubricating film. Formula 4-Stroke® Synthetic Oil also contains robust anti-wear additives that further reduce wear in metal-to-metal contact regions While automobile engines normally operate at around 2,500 rpm, outboard motors can run twice as fast, requiring greater levels of wear protection and better bearing durability than automobiles. In addition, prolonged idling and low operating temperatures contribute to fuel dilution, further thinning the oil. To ensure adequate protection for their engines, marine engine manufacturers set minimum high temperature/high shear (HTHS) viscosity limits. AMSOIL Formula 4-Stroke® Marine Synthetic Motor Oils are shear stable and formulated with sophisticated oil additive chemistry, exceeding the HTHS requirements of both the API and NMMA FC-W

Engine Oil Formula 4-Stroke®

Marine Synthetic Motor Oils (WCT,WCF) are formulated specifically for use in 4-stroke gasoline-fueled engines used in marine applications. They offer unsurpassed wear protection, viscosity stability, low volatility and excellent low temperature fluidity. AMSOIL Formula 4-Stroke® Marine Synthetic Motor Oils meet the “Warranty Certified” status of engine manufacturers. They are recommended for use in 4-stroke outboard motors including Honda, Yamaha, Mercury, Suzuki, Johnson-Evinrude (BRP) and more. Also excellent for use in marine inboard/outboard engines, marine inboard power plants and personal water craft.