Using thicker oil to try and cure a problem is like slapping on a ton of underarm deodorant cause you stink and really need a shower. I can understand you need it but that's simply not the right way to go about it. In an evening you could easily pull a valve cover and investigate things. Just make sure and have a gasket scraper, roll of shop towels, can of brake or carb cleaner, and a new set of valve cover gaskets and there should be no problem yanking the VC, investigating things and putting it back together so you can use it the next day.