2005 e320 cdi dirty engine oil
 

with 110k. I'm the second owner as of 98k. Changed the oil at 104k (it was changed at 98k before by seller.). The oil was and is black. I've had diesel pickup trucks but never let the oil get that dirty. I'm thinking of changing it 2x in a row just to clean up the crankcase and then again in a few thousand. Is this a good idea or not necessary?

I did an oil change at 300,000 miles on the dot. 3,000 miles later and the oil is black. I think that may be normal with diesel engines.

My 85 only has 165K on it. The oil is black 500 miles after I change it. I don't even give it a second thought.

I have tiki torches in my backyard that I fill with diesel fuel. They put out a TON of black smoke, but I don't care. A gallon of diesel is what, $2.35? A quart of torch fuel is 8 bucks. I figure that dirty oil is just what you get when you drive a diesel.

My car only smokes during full throttle acceleration. The rest of the time you don't see a thing.

I'm betting the seller let past services go, this is evidenced by them changing it just before you bought it.

Last year the company I work for bought a used backhoe without me looking at it. The company is a manufacturing facility and those that went to look at it know nothing about machines besides it was sort of shiny. The dealer changed the oil after we bought it but before it was delivered. By the time I looked at it 10 operational hours had passed, the oil was as dirty as any I had seen, and this is an electronic controlled engine.

Modern diesels have much better fuel control and piston ring seal so oil contamination with soot is less of an issue unless service intervals are let go.

I'd change the oil now, push the next oil change to half distance then reassess 1/2 way through that oil change. Changing 2x in a few miles would be a waste of oil, you need time for the oil to load with soot. ( RE: hot oil splashing around cleaning things out. ) I would not use any sort of motor flush, the soot was deposited slowly over time and must be removed slowly over time.

Most diesel engines have extremely black engine oil even immediately after an oil change. That's normal. Just make sure you continue to change it at the recommended intervals.

Slightly off subject and about a different engine. On the 617.952 if you look at how moch Oil you are supposed to put into a new Engine and how much oil you replace during an Oil Change there is a whole 1 liter difference.
That means when you do an Oil change there is one liter of old Oil inside the engine and the Oil gets balcker sooner.

Older MB Diesels
 

with remote mount Oil Coolers NEVER have a complete oil change UNLESS
the owner has mounted a valve in the OC line to allow such.

There is/was one guy here that cracked open one of his Oil Cooler lines
(At the bottom of the OC) every time he changed his oil.
[I can't remember if he reported "Cleaner Looking " sump oil or not]

Folks, diesel oils are engineered with a huge dollup of solvents/cleaners, hence they blacken right away. Use to use DELO in my old big block Chevelle, and it would blacken in 3-4 hrs runtime. Now I use regular gas engine oil ( high zinc) and it stays clean all summer.

Its the oil formulation. You put a reg non-diesel oil in ( as a pro tech did on our "new" 95 before we bought it - with 5-30w no less! ) and it wont blacken so fast, if hardly at all.

Diesels produce a lot of carbon. That's also why you'll have "dirty" oil after an oil change and 10 miles later.