I have had my 300SD for 2 1/2 months now, and I am trying to get a feel for how much oil she uses. I did an oil change first thing when I bought her, that was about 2k miles ago. At about 650 miles after the oil change I needed to add a half quart. Then about 800 miles later I added another 1/2 quart. I have noticed that when the eng. is running first thing the exhaust (at idle) is tinted blue. However after she has warmed up the blue smoke appears to go away. So I am figuring it's the valve seals that are leaking when she's cold and sealing up when hot. There is however, no puff of smoke when she is started first thing. Which is the usual sign of bad valve seals in a gasoline eng., but I don't if diesels are different in this regard. So is this oil usage seem normal, and nothing to worry about considering the 225K miles on the eng. I am using Castrol GTX 20W-50 per the recommendation of the MB/Porsche/BMW ind. shop that I bought the car from. They use this oil, change it every 3K and she'll run forever.

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member