J/30 Class Association Forums J/30 Forum The Boat, Sails and Equipment Favorite motor oil?

Oil Viscosity should be as recommended in Yanmar Service Manual for outside temperature ranges - SAE 10W-30 will cover you for most of North America for year round use. If the water temperature is above 95 degrees, use 50W oil. The service grade should be SAE CB or CC for moderate duty diesel engine service.