Rotella T 15w40 made mine sound like an industrial sewing machine. I'm currently running Valvoline 10w40 MaxLife... seems fine... goes in clear, comes out black after 3k miles. I do loose about a qt every 1500 miles on the dot.
Mine knocks like crazy... hoping the Valvoline engine guarantee covers the repair work..if not, oh well, still needs to be done anyway.