Synthetic D4 ATF Our most popular and versatile ATF, D4 is suitable for use where Dexron III, Dexron II, or Mercon fluids are recommended. D4 ATF is designed to satisfy the improved low-temperature requirements which will be in the new Dexron IV specification, and the improved shear-stability requirements which will be part of the new Mercon specifications. D4 ATF also provides a GL-4 level of gear protection, making it a superior product for transmissions and transaxles like the Corvette's T-56. The balanced frictional characteristics provide smooth and consistent shifts for extended drain intervals. The superior stability compared to petroleum ATFs allows high-temperature operation without varnishing valves and clutches which leads to transmission failure. It's stability allows high-temperature operation without varnishing valves and clutches. Also provides improved shifting in cold weather.