I had noticed a similar situation with mine a few years ago, and it was traced to a leak in the front engine cover(?? for lack of a better term). That belly pan under your car is great protection in case you drive over those concrete parking lot berms that would otherwise trash your oil pan, but it also may conceal all but the geyser-like leaks under your engine. This is supposedly a common source of oil leaks for this particular model.
Once I got mine replaced, the oil consumption was dramatically reduced!
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car