Just changed the oil on the E500 (37.5k)...the oil and 1250mi 95% freeway use- on it. Oil from the dip stick looked clean- just slightly dirty brownish...however when drained- the oil looked black as the 'Ace Of Spades'
fyi- I use 15W-40 Pennzoil dino and Mann filter (from Mercedesshop)
Also just changed the oil on the E320 Coupe (97k) and it had 3200mi 90% freeway use-on it. Oil from the dip stick looked much dirtier (vs. the E500) and looked jet black when drained (smelled worse too).
fyi- I use 20W-50 Castrol dino and Hengst filter (from Mercedesshop).