Now heres one I have not hear b4..took my mowers in to my new service dealer(they sell exmark,scag,jd,...by no means a fly by nite operation) and he suggested using a diesel rated oil for the mower engines...I said huh? Says they put this oil in all the commercial mowers they service, except for one company and that company wants std oil, non syn. I wish I could remember the actual specs on the oil but I believe it was a Havoline product.He says the companies really like the results with this oil. DiD a search here and could not find anything in the titles on d-oil for air cooled engines. I was going to go with Pennzoil syn until he threw this curve ball at me... Told him to hold off on the oil change until I checked in here.Any info/opinions on this are appreciated..