Low oil pressure warning light.

My low oil pressure warning light came on and I took the car to the dealer for a look see. He told me that the oil pump/filter were ok but that he had to put 5 Qts of oil into the engine to top it off.
Being down 5 qts out of 8 makes me nervous and I feel as though that's unusual. I'm within the oil change mileage range still, there's no oil puddles underneath the engine, and I haven't noticed any smoke when the car is running.
What's happening?

Peter