Ive developed a bad engine oil leak from the bellhousing area on my 99 7.3. No major leaks up in the valley or under the turbo, the rail plugs area on the back of the heads are dry. Just some "sweating" around the HPOP and that's about it....unless I'm missing something?. I switched to synthetic 5w-40 Mobil Delvac aprox 14000 miles ago and would like to keep running it for injector longevity and better cold starts. It just started leaking less then 500 miles ago now. Is there anything else to look for other then the rear main seal? Its leaking a drip every 5 seconds or so. I might switch back to 15w-40 to see if that helps. Not looking forward to doing a rear main seal in winter out in the snow.