I have an 02 E350 with the 7.3 and 85000 miles. Recently is has started using a lot of oil, maybe 1 gallon in 300-400 miles. After much research in this forum most state that the injector o-rings have gone bad. I checked the fuel filter and it is normal in color, no oil contamination. There are no visible leaks anywhere and no smoke coming from the exhaust. I noticed recently with the oil filler cap off a lot of blowby is coming out where there was little to none before. Engine runs fine and fuel mileage is consistent. Any ideas?