We're having the major fuel system problems with our 2006 - 2007 F-750 diesel fleet. Ford blames gas additives but our other trucks from different manufacturers have no problems, though they use the same fuel. We have 5 F-750's with the same problem and over $25K in fuel system repairs over 12 mos. In each case the first related repair occurs between 35 and 39,000 mi. I know a company with a larger Ford truck fleet which solved their related problems by replacing all their truck fuel tanks. I am speaking with a Ford customer service person now, but judging from the other review, I am not optimistic.