Experienced boaters grab Mercury® Marine 4-Stroke 25W40 Synthetic Blend Marine Engine Oil. This proven boat oil outperforms automotive oils in marine applications because of its specialized additive package just for marine engines. Continued use of Mercury Marine 4-Stroke 25W40 Synthetic Blend Marine Engine Oil provides the best wear and corrosion protection when operating the engine at maximum output and high temperatures for extended periods of time; maintains peak engine performance and reliability; and eliminates thermal breakdown under extreme RPM, temperatures, and load. Unlike inferior, traditional marine oil, This Mercury marine oil won't damage emissions systems and works great in any marine engine with or without a catalytic converter. For use in 4-cycle outboard engines. Superior corrosion protection. Most recommended OEM marine engine oil. The best wear and corrosion protection, even with high engine use. Maintains peak engine performance and reliability. Eliminates thermal breakdown under extreme RPM, temperatures, and load. Won't damage emissions systems. Works great in any marine engine with or without a catalytic converter.