Great posts on the oil cooler. I bought my Dodge Sprinter 3500 used, had about 45K on it and the oil was filthy. I drained the oil/removed the filter. I then filled the crankcase with 3 gals of kerosene, let it stand for a few hours, then just nudged the starter to turn over the engine a rev or 2. Let it stand a few more hours then drained the kero. After it drained, I used a coat hanger wire wrapped with a cotton cloth strip to sop up any remaining oil/kero in the oil pan, via the oil drain plug. When the strips showed no more oil/kero, I put in about .5qt of Walmart synthetic (it is cheap), and let that drain thoroughly. Then added the Mobil1ESP MB formual synthetic. After driving 2K+ miles, the oil still looks good, somewhat dark but doesn't look like "gunk". I have 65K on it now, and I am hoping this method keeps my oil system and cooler somewhat clean and functioning properly.
walt