Mercury - Automatic Transmission Fluid Marine DEXRON III Formula 1 Gallon 8M0173230. Overview. Anyone who spends real time on the water knows there's a difference between products designed for land vehicles and those built from the ground up for marine life. Mercury Automatic Transmission Fluid 8M0173230 falls squarely into that second category. It's made for the long days, the towing loads, the tight maneuvering in a crowded marina, and the quiet confidence you feel when your transmission shift