since draining out royal purple 15w40 and filling with rotella t6 5w40, i hear a slappy chatter towards the bottom of the engine on the drivers side when it is first cranked up. It progressively quiets down as the engine gets up to temp. I wondered if the lighter cold temp weight of the 5w40 is the reason. It runs fine but i almost want to go back to 15w. Just curious if anybody running a 5w has noticed similar sounds.