I don't exactly agree with MB's definition of "normal", but they will fix the problem, provided you play by their rules. Most importantly, you'll need to prove that the service schedule was followed, or at least that the oil and filter changes were done on time. In your case, it shouldn't be a problem, since regular maintenance was/is covered for the duration of the warranty period. A simple VMI will show the mileage and date of when these services were performed. As long as the previous owner paid attention the service reminder, you're half-way there.

You may not have a relationship with your local MB dealer, but you need to start one now. The first step is to begin an oil consumption test. This involves your dealer performing an oil and filter change, re-setting the FSS counter, and recording some data from your cars' "memory". After this is done, simply drive your car as you normally would, adding oil when necessary. These oil replenishments are recorded in memory, along with mileage information. When the consumption rate meets MB's criteria for excessive usage, the dealer can go to bat for you.

In most cases, they'll fix the problem at no cost to you, given the mileage on your car. Good luck, and let us know what happens.