Hopefully you don't have a really bad problem considering the slow leakage. It's interesting that you have oil in the coolant but not coolant in the oil. I thought the coolant typically operated at higher pressure than what is found in the crankcase, so the natural flow would be coolant into oil. Would be interested in hearing other's thoughts about how oil gets into coolant. (Maybe during cooldown somehow?)

Not to start an oil jihad - I use Shell Rotella T dinosaur oil with STP oil treatment (said to be a synthetic additive). Oil and filter changed every 4,000 miles, a daily driver - 150 miles/day.

I hereby issue a fatwa against using synthetic motor oil in diesels.

:p

Ken
1982 300D
310K miles