For what it's worth, I'm a tech and see nothing but merc. and bmw, many merc. have oil pressure readings like this. If you've changed the oil and filter and seem to have no other oil pressure problems I wouldn't worry much. We've yet to have a customer complain about pressure to high, so we rarely look into it. Does the needle move/twitch at all, esp. when shifting into or out of gear? idle up/down? Hope this helps.
MV