Mileage?

Valve Stem Seals and or Guides worn. Rings, Cylinders and Pistons worn.

There is limited ways for the oil to get into the Combustion Chamber. It has to come up from the Crankcase, get in through the intake Air, past Valve Stem Seals/Guides and there is one other place a few Member have said. (On the older models if the Diaphragm on the Vacuum Pump goes bad Oil will get into the intake manifold.)

They said if the little O-ring in your Fuel Supply/Lift Pump is shot Oil can be sucked into and mixed with your Fuel.
Because more Fuel goes back to the Fuel tank then into the Engine if the above is happening you would expect your Diesel Fuel go be off color; kind of a translucent gray.

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84 300D, 82 Volvo 244Gl Diesel