Marine engines are often operated in harsh, saltwater environments that are much more demanding than the conditions faced by most automotive engines. Accordingly, their engine oil must be up to the task. Pro Star Super Premium Synthetic Blend 4 Stroke Oil is specifically designed for high performance 4 stroke outboards, gasoline inboards and stern drives. One of the first 4 stroke oils to be certified under NMMA’s new FC-W category. Meets or exceeds all criteria for viscosity, filter plugging, foaming and aeration. Successfully passed NMMA’s 100-hour general performance engine test.