No special oil. I use whatever I can find in my 4.5 hp Briggs from k mart. Been mowing with it since 1993. Probably has 5w30 in but who knows. Haven't changed it for years. I don't care because it runs and starts every time i need it. In 26 years it just needed plugs, filter, starting cord and control lever repaired, and self propelled belt tightened. I check the oil in spring. It's full so I mow. Someday I might buy a new one.