Mobil Super 5000 and MaxLife blend were two of the smoothest/quietest oil I used in my vehicle, so I would suggest trying those. Though I've also heard good things about Quaker State Conventional and Motorcraft oil, so it might be worth trying those as well.
If you want to move up to a full synthetic, Valvoline SynPower was the smoothest/quietest in my car, with PP coming in second.