Quicksilver's 4-Stroke oil technology outperforms automotive oils in marine applications because of it's specialized additive package designed for marine engines. 5W30 Full synthetic meets the requirements of the API SN Engine Oil Service Category (BEST Choice). For use in all 4-Stroke marine enginesEngineering approved for Outboard, MerCruiser, High Performance and Stern Drive/InboardExceeds all Marine industry 4-Stroke oil requirementsFlagship engine and corrosion protections-Industry leading strength and viscosity retention and ultimate corrosion and wear protectionThe most recommended marine oil-over 5 years of engineering and development