Fully synthetic straight 30-weight engine oil is formulated for Volvo inboard & stern drive marine engines. Sierra full synthetic inboard engine oil SAE 30 5 quart bottle Recommended for gasoline and diesel inboard and I/O engines Developed specifically for the marine environment and the high running stresses marine engines encounter Reduces friction and wear for long engine life Beter lubrication effectiveness for longer durations than mineral oils Reduces oil consumption and improves fuel economy Exceeds all FC-W requirements API-CF/SL