Sierra 25W-40 FC-W 4-Stroke Stern Drive Oil is formulated to provide superior lubrication and corrosion protection. Stern drive and inboard engines operate under high load and running stresses, so Sierra developed their oil for the marine environment and will outperform standard 4-cycle automotive engine oils. Sierra oils offer strong detergency, anti-oxidants, antiwear, corrosion protection and reduced wear to the internal components. Excellent low temperature operating properties. NMMA FC-W Certified, recommended for use in Mercruiser and OMC.