It is NOT the synthetic oil. My 300E was burning a quart per 400-500 miles when I got it and it was running on dino, I switched it to synthetic, same thing. It was fouling plugs with oil as well. So I paid the $$ and had the valve stem seals replaced, and it now burns virtually NONE between 4,000 mile changes. I did the oil change on it in July, and it has traveled over 3,300 miles since then....oil level has not changed at all on the stick.

Get those stem seals replaced! And run a good diesel synthetic oil...the M103 loves it. My old stem seals were hard as rock, and probably doing next to nothing. The new ones are made of viton and last longer, and are much softer.

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)