Dad started our Ford 1715 up a couple of days ago, and did something it's never done before. It started blowing oil out the breather tub that connects to the top of the valve cover on top of the engine. Not just a little bit. The oil was streaming out. I checked the oil today and it's almost to the top of the dipstick, way beyond the "full" mark. It also looks very thin and smells strongly of diesel. So I'm guessing fuel is somehow making it into the crankcase while the tractor is sitting. Any ideas what might be wrong?