I have a 2002 H6 3.0 with 153K miles that has a worsening oil leak. There is oil dripping from somewhere on the passenger side of the engine, towards the rear. No overheating issues, and HG was fine at last inspection. I looked at the oil cooler/oil filter area, and there are no signs of a leak there, nor in the pan. So it's probably the valve cover gaskets, but can one side wear out quicker than the other side? Because that seems to be what's happening here. Or am I missing another potential leak site?