Mercury - MerCruiser 10W30 4 Stroke Engine Oil 8M0078626 This 10W30 engine oil is designed for use in 4-cycle outboard engines. This oil helps provide superior corrosion protection to your system in your system to help extend engine life. Help maintain your peak engine performance and eliminate thermal breakdown under extreme rpm, temperatures, and loads. This oil can be used in any marine engine with or without a catalytic converter and will not damage emissions systems. California Residents WA