I've been reading the oil debate and don't want to start that again. Actually it's all very informative. I have a slightly different issue. I have a '73 220D which I've owned for 14 years. Used regularly for 10 years; sat up 2 years; changed oil regularly and always after it had been unused for a while; been using it a couple of times a week for the last 2 years. I now want press it back into more regular service. Drained the oil and the oil cooler. The oil is getting dirtier at oil changes; blow by? lack of use? I'm not sure why. I'm toying with the idea of putting synthetic in it to clean it out. Also, somewhere along the line I used synthetic one winter because it started hard and the synthetic clearly allowed the cold engine to spin more freely with less drag. I sort of want to experiment with Mobil 1 15-50 over against my usual Cast 20-50. I've always resisted changing oil brands (I've always resisted changing in general), but this might be an interesting time to try something different. Making some mistake that I haven't forseen? Cutting loose the sledge that's holding the old girl together. The new service involves a 300 mile trip to another location and leaving the car with my wife (who I still love) as her primary mode of transportation around town.
Thanks as always for any information.

As far as what ive read,oil getting dirty real quick
is the result of combustion by products sipping into
your comb.chamber.Maybe loose valve guide,or seal.
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Clauser1

I agree with Clauser1, there is something wrong beyond which oil you are using. It would be better in the long run to get it fixed. Also, there may be problems changing to synthetic in an older engine. The main reason for this that over the years regular oil can leave a film or varnish over the more important seals and gaskets. This film acts as a seal itself. Synthetic doesn't do this and cqan wear that varnish away, revealing oil leaks that the varnish was preventing. If you really want to clean your eninge, find the problem, get it fixed and then try an engine cleaner. I am pretty sure that both Molly oils and Redline have an additive you put in your crankcase a few hundred miles ahead of an oil change. Drive around while this cleans your engine, and loosens the sludge and alot of the other garbage. Then drain the oil (maybe even overnight as Larry Bible does - this gives the sludge more time to ooze out). That should have you fixed up pretty good.

Switched to Mobile 1 Delvac
 

I change over to Mobil 1 Delvac (snythentic), with 150K miles on he car and have no leaks or problems. I did a lot of research on this before I switched and all I could find was some cars would leak a little, but most cars do anyway...

ps: I switched to Mobil 1 in my Landrover and it gets more MPG..

Something Else...
 

You might want to run a bottle of Redline Diesel Fuel Catalyst or 85+ through the fuel system if you haven't already. Use 1 whole bottle for the first tank of fuel, and 1/3 per tank until time for your next oil change. See if it doesn't help clean up the amount of crud. It may take driving the car a little harder, and a couple of oil changes, but I wouldn't be surprised if it cleaned up your engine...

I use Mobil 1 15w-50. I dont use any oil or have any leaks.

1) Get your engine fixed first
2) Check and change your gaskets before switching.
3) Use a engine cleaner first
4) Switch to Mobil 1 and enjoy

You said you used Mobil 1 over the winter once right? well did you have any problems then? If not, continue to use it.