15W-50 Full Synthetic Oil Quart Bottle Briggs & Stratton new Vanguard 15W-50 full synthetic engine oil, specially engineered for engines installed in commercial equipment and continuous-use applications that are operated in high-temperature environments. This oil is designed for ambient temperatures between +20°F (-7°C) to +130°F (54°C), making it an excellent choice for commercial cutting equipment and other demanding operations exposed to high-temperature conditions.