Checked my oil level the other day and I was down by about a quart and a half. I use Mobil One 10W30 synthetic and change it every 5K or so. This check came with about 4K on the current oil. Car is my daily driver. Any reason why my car would be drinking oil like this??? Is this a common occurrance??

 

could it be the pcv system? check in your intake manifold and see if you have a big oil slick in there