Well in 7 years of ownership , Our 55 has asked please put 1L of oil in the engine next time you fill up with fuel only twice , that's about 50k of motoring. I do have the oil changed even year with the MOT .
After 12 months (including serviced early (at 10 months) to coincide with MoT ) and 6000 miles the car has taken less than one litre of oil.
My R171 was equally frugal, and from memory so was the (vanishing memory) R170.
For all their (many and varied!!) foibles Mercedes I believe, do not burn oil, unlike some VW marques I've encountered, or leak oil, like a certain brand new Porsche some many years ago!