My oil seemed low about a week ago - it was at about the midpoint on the notched area on the dipstick. I drove about 800 miles and then went in for an oil change. They said it was very low (only showed up at the very tip of the dipstick) and found oil all over the underside of the hood and all around the engine compartment. They could not find any leaks anywhere and said it seemed like it was leaking at the oil cap. The cap was on tight. They changed the oil and cleaned up the spilled oil. I cleaned it even further myself and then drove about an hour. When I checked again, it seems like oil is leaking out around the cap. Can this happen? Should I replace the whole cap, or can I replace the rubber gasket? Could it be coming from somewhere else? Thanks.