Mercury FC W 25W 40 Marine Engine Oil - Gallon - 92-8M0078628 Mercury's 4-stroke oil technology outperforms automotive oils in marine applications because of its specialized additive package designed for marine engines. 25W40 is recommended for all marine engines. Things to know about this oil: For use in all 4-stroke marine engines. This oil is engineering approved for all marine 4-stroke applications including: outboard, MerCruiser, high performance, stern drive/inboard. Exceeds all marine industry 4-stroke oil requirements including FC-W and FC-W compatability. Outstanding engine and corrosion protection - industry leading strength and viscosity retention and ultimate corrosion and wear protection. The most recommended marine oil. More than 5 years of development work by the largest marine manufacturer in the world.