I have the same issues I love the car, Mercedes installed all these emissions parts even installed a new turbo. Stillburning 2 quarts on a full tank of gas 642 miles.
Im going to try Valvoline restore and protect .

 

I'm also trying the Valvoline Restore and Protect. I figure there is no point in protecting the DPF if the engine is burning that much oil.

I also found a leak and just fixed it. So we will see if the consumption goes down significantly. Now that school is back in session it will get more miles, but when I fixed the leaking oil filter housing it lost some oil, so it threw off my measurements.

I will report back after another 600 miles.