Took my 2003 F-350 Diesel into service dept for warranty reapir. Truck had minor oil leak after only 21,000 miles. They said that that oil was traveling up, yes, up my cold air return pipe because I had a dirty air filter. Huh? At first I thought the backpressure might be enough, but anyone with a logical mind has to realize that the laws of physics still apply to Ford motor oil. What a joke. I finally gave up and took the truck to Willey Ford and they replaced the high pressure oil pump and guess what.......no more oil leak! It's a miracle! Butterfield is special, in a short bus kind of way. Do not go there!