Mark,Please read the manual on that engine. The 250 Pro XS is set up to run the Mercury/Quicksilver “Premium Plus” oil.In fact, I have been told by more than one Mercury master mechanic NOT to run the DFI oil in the 250 Pro XS. Sound to me like your dealer is shooting you straight on this one. Ive had great service from mine, and it has never seen anything but Premium Plus oil, and 87 or 89 octane fuel.Mike Whitten/Germantown,TN