It has come time for another oil change. It's a 1984 Ford 1310. The tractor sees about 15 hours of use a year, as in it has a total of 544 hours on it. The oils gets changed every three to four years. I do, however, try to make sure the engine reaches operating temperature whenever I run it. There are so many oil choices and was wanting some recommendations on a oil that does well under these conditions. The tractor takes a whopping 3.5 quarts, so cost isn't that important. Thank you.