Synthetic blend 25W-40 engine oil is formulated for stern drive & inboard marine engines. 5 Quart 25W-40 Synthetic Blend Inboard and Sterndrive Engine Oil 4-cycle oil is blended with premium grade synthetic and mineral base stock combined with superior design additives formulated for the stress endured by sterndrive and inboard engines Superior corrosion protection Advanced lubrication for reduction of wear to internal engine components Outstanding friction reduction and wear protection Removes thermal breakdown under high RPM's, extreme temperatures and loads Extensively tested for outstanding performance NMMA FC-W certified/API-SL