I finally switched my 300D to synthetic on June 28 with 171729 miles. I am now at 172453 miles and my car still does not drip any oil. The rear main seal does/did leak a little bit due to a once overfilled crankcase, but the leak is slow enough and I drive enough that any fluid is simply blown off of my engine. My car never sits long enough to accumulate a drip.
Also, the oil pan gasket has/had a slight leak, but I only noticed this on 6/28 when I was in the process of changing my car to synthetic. I will update this post when and if I notice any changes.
My leaks must be extremely slow. Although the bottom of my engine is slightly wet, my car never drops anything on the ground.
1976 300D (W115) - 330K and still going (sort of)
1991 300D 2.5 Turbo - Sold at 221K
1983 280SEL - Sold at 206K
1981 300SD - Sold at 232K