What type of oil should I use in my Westerbeke or Universal engine/generator?
Use a well-known brand and try to use the same brand each time you change the oil. Avoid mixing brands of oil. Different manufacturers use different additives, and mixing brands may cause a problem if additives are not compatible. More important is to use the correct A.P.I. (American Petroleum Institute) and S.A.E. (Society of Automotive Engineers) ratings. For Westerbeke and Universal DIESEL models use A.P.I. code CF or CG-4, S.A.E. #30, 15W-40, 10W-30 or 5W-40. For Westerbeke GASOLINE models, use A.P.I. code SJ, S.A.E. #30, 15W-40, 10W-30 or 5W-40.