2002 F350 7.3. 190,000 miles. Losing a quart every 30 miles when pulling empty 40 ft gooseneck. Losing hardly any when driving just the truck. Fuel bowl is clear. No oil in turbo lines . No smoke and tail pipe is not wet. No visible leaks. No oil under body or on the bumper, tailgate, or trailer Took oil cap off and very little blow by. Using delo 400 15w-40 since new Ford mechanic said three cylinders were low on compression and may have stuck rings .I ran a quart of transmission fluid per tank for a couple of tanks with no change. Truck runs great with no loss of power and no turbo noise.