master1917,
Not to understate that kind of oil consumption in ~ 700 miles, but were you poz that the oil was full, on the stick, when you got the car?
Dlr oil changes range from pricey & OK to lame, in my experience...some to many techs have no memory and don't check the crankcase quantity.
Just an idea, before you go crazy chasing oil issues, and GL with that V8 M.
GL, mD