don't sweat the small stuff, e250 is a 3/4 ton + , for 550 you can deal with the small stuff. My first test for any gas motor is the ol finger in the exhaust pipe ( after looking underneath to see if it's all there and no bad leaks anywhere ), if it comes out clean, cool, if it comes out black, leave it. Hek, at 550 you'll get most of that back when you scrap it ; )