Mercury - Automatic Transmission Fluid Marine DEXRON III Formula 1 Quart 8M0173229. Overview. When you spend your days on the water-towing wake riders, cruising across calm mornings, or pushing through wind-chopped afternoons-you start to appreciate the parts that quietly keep everything running smoothly. Mercury Automatic Transmission Fluid 8M0173229 is one of those unsung essentials. It's engineered for the constant shifting, heat, and pressure that marine transmissions endure, and it gives yo