That's a good idea but I think that it's only a temporary fix. Like mentioned earlier a plug or something could've not been put in or came loose. It could be a bearing clearance issue or a bad oil pump and possibly the lifter bores could have excess clearance. I don't mean to sound negative here or anything but I think that your not to far from having to take it apart and see what's going on. True, the thicker oil will help for a while but if it's a clearance issue or the pump is bad it will only get worse over time.