My engine started leaking a lot of oil yesterday when i made a 850 mile trip. Before yesterday, the oil level didn't change noticably between oil changes, it may have had a slight leak but nothing to worry about. But yesterday, it lost more than a quart of oil (over 850 miles) and when parked after I arrived I could see a lot of oil under the car. I am not totally sure, but i think it is coming from the rear of the cam shaft. It also seems to be leaking slightly from the oil fill cap onto the cam cover. The front seals are fine, and i canged the rear main seal when i replaced the clutch less than a year ago. It seems strage to me that it would change that quickly. Is it common for this seal to fail in this way???

Thanks, Mark