" have been told from my dealer that the Tolerance level for which BMW have set for there engines is
1000miles per Liter of Oil Is this really true? "
I wouldn't be a bit surprised if this were true Rams Have noticed mine drinks the oil like it is going out of fashionl!
That's what the Dealer states, it's not necessarily BMW's opinion

The
MCS is very frugal with oil, if you have excessive oil consumption then you probably have an oil leak