Sierra Marine 25W-40 4-Stroke Conventional Marine Oil 25W-40 4 STROKE MARINE STERN DRIVE ENGINE OIL has been formulated to provide excellent lubrication and corrosion protection. Stern drive and inboard engines operate under high load and running stresses. This product is developed for the marine environment and will out perform standard 4-Cycle automotive engine oils. Sierra 25W-40 oil offers excellent detergency, anti-oxidants, antiwear, and corrosion protection. The benefits to your engine ar