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 Star Tron Lubricants 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 NMMAs new FC-W category. Meets or exceeds all criteria for viscosity, filter plugging, foaming, and aeration. Successfully passed NMMAs 100-hour general performance engine test.