Mr. Bill, I have used the Advanced Auto Parts 15W40 as well as other generic and house brand 15w40 oils with good results. They are probably bottled by one of the major companies, just without all the advertising costs added on. Right now I am using Coastal 15W40 Fleetoil from Autozone for $3.99 a gallon. I have also used Pep Boys 15W40 housebrand. Just whatever is handy.