Since I am waiting for parts to continue my turbo engine installation project I thought I would poke around the engine while it is on the garage floor and easy to access. I checked the turbo, and it has no end play, and spins fairly freely, but the compressor wheel is a bit black and greasy. What's up with that?

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine