I had the same exact problem with my 84 190e (94404 miles) prior to my owning it it was my grandmothers and i would do basic mintainance chorec on it you know;plugs, oil,airfilter. The first time I chaned the airfilter was before I took up the basic maintainance work on the car. I had been looking under the hood and happened to open the air cleaner housing to check the filter and found that it was nearly 75%oil soaked I knew this couldnt be good so I showed my grandmother the filter and explained that te filter needed replacement, she agreed and I replaced the filter with one I had to order at Murray's discount autoparts (my local general parts store) while I was in the store ordering the new filter I was thinking about the oil in the filter and how i could stpo it from getting there again. Anyways I saw a breather filter hanging on the rack and thought to myself that the flossy filter material would act as an oil catch and yet still allow the valve cover vent to do its job. I bought a breather filter (like 5 bucks) and took it home. I had to cut the filter material to the cottect size to fit the small breather hole compatment inside the air cleaner housing. Since I put the breather filter in the air filter hasnt gotten a bit of oil on it and this was almost 2 years and a few airfilters ago. Since becoming the owner of the car Ive switched to a K&N filter, no its not for a preformance gain just economy since the fram filter was only like 10 dollars cheaper than he K&N, I still have the breather filter element in the air cleaner housing and the oil stays in that filter instead of my airfilter

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1984
190e 2.3L
107000 miles