if you're suspecting oil at all, why not just go ahead and change it? walmart wont do it, even if you haven't done it in a while I think you can handle it. one bolt, I never even use a wrench for the filter, I can get it w/ my hand.
I know when I go a couple hundred miles too long for an oil change, you can hear a kind of click/ping coming from arond the same area you're talking about. after an oil change it's like a while new car, and I hate myself for procrastinating. bleh.
