Bad turbo seals can suck a lot of oil but you'll see it. My truck blew the turbo seals and blew a gallon out in about ten miles.... I definately saw that. I doubt that's your problem. Have you read this post? Oil consumption 602/603

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1985 300D Turbo ~225k
2000 F350 (Powerstroke) 4X4, SWB, CC, SRW, 6spd ~148k
1999 International 4900, DT466e (250hp/660 ft/lbs), Allison MD3060 ~73k