Some S65s consume a liter oil per 1500 miles (the ost extreme I've read about thoug), some consume close to nothing. As your sump was filled up recently, work your way back and see if 1.5 liter seems within reason. If not, I'd personally start all over by dumping the oil and refill to avoid over fill.
This bloody sensor... mine has treated me ok during my 6 years but I have experienced very strange behavor after oil change, such as showing decrease after top up...
