[thstone]

7 quarts per 5000 miles is 714 miles per quart.

Porsche spec's excessive oil consumption at 600 miles per quart so while your experience is certainly on the higher side, Porsche would say that its within the range of expected oil consumption.

In regards to where the oil is going, there are only a couple of places it can go: external, coolant, or combustion chamber.

If there are no external leaks and the coolant looks clean, then its most likely going into the combustion chamber. Pull a couple of spark plugs to confirm. If this is the case, they will be coated in oil (whereas they should normally be a dry tan color).