BG 244. Half a quart in a full tank of gas every 10K miles or so. Just used it recently for the first time and immediately felt the engine running smoother. MPG increase was slight but absolutely a smoother/quieter running engine. Not sold at your local auto parts store but is avail on Amazon -
https://www.amazon.com/BG244-Diesel-...dp/B00K0WR7VI/