I recently replaced the air filter in my 82 300D and noticed some oil in the air filter. After a few weeks I checked the new air filter and there's a little bit on that too. Also i've noticed some oil leaking from that side under the car.

Is this the turbo going out?

If so how do i check it?

I doubt it has anyhting to do with the turbo. So you are safe.

There is a return line for oil collected here that goes down to the crankcase.

Do get the engine clean on that side and watch carefully.

Either the return line is not seated or sealed, could possibly be plugged.

But to start with, remove the air cleaner housing and clean it all up,
study the tube that runs from the bottom of the air cleaner housing to the crankcase.

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80 300D 340K Owned 30 yrs
83 300SD 440K Owned 9 yrs - Daily Driver 150mi/day
02 Z71 Suburban 117,000
15 Toyota Prius 2600 miles
00 Harley Sportster 24k
09 Yamaha R6
03 Ninja 250

Blowby coming from the EGR. Another good reason to clamp that pesky EGR off.

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http://superturbodiesel.com/images/sig.04.10.jpg
1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42

The diaphram in your vacuum pump has a hole in it. I had an 80 300CD that had oil in the air breather too. Alot of it. Found out the bad diaphram was allowing oil to pass through it and get pumped to places where only air should go. Replacing the diaphram is easy. The pump is located on the driverside at the front of the engine. Lower side.
The bad news is that while oil was being pumped into your airbreather, chances are that oil was also being pumped into your vacuum lines leading into the passenger compartment. Look under the dash around the steering column for a vacuum dashpot. Pull the vacuum line from it and see if oil is present. If it is you may have to clean all of them and their lines.
I had to open up and clean alost all of my dashpots and replace the lines with those I got at the junk yard.
Good news though, after I got the job done my vacuum system, locks, shut off, etc, work so much better.

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Selling used Mercedes parts on Ebay...always changing...
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