Castrol ATF Dex III is an automatic transmission and power steering fluid for use in GM automatic transmissions pre 2005 and in many automatic transmissions in a range of makes and models where Dexron (II or III) or Mercon performance is required.


It is fully compatible with earlier Dexron and Mercon type fluids and maybe used for topping up or completely replacing it.

Castrol ATF Dex III is dyed red to distinguish it from engine oils should leakage occur.


  • Enhanced high temperature performance giving improved and more durable shift feel on gear changes.
  • Increased resistance to oil oxidation and degradation. Increased clutch band and clutch pack capacity.
  • Improved protection of copper and bronze components. Improved low temperature fluidity compared to Dexron IID, Dexron and type Suffix A fluids.
  • Longer transmission component service life especially in high load applications
  • Enhanced life of copper alloy based components and improved fluid service


  • Dexron® III H, IID and II.
  • Holden HN 2126.
  • Mazda M III Fluid.
  • Ford Mercon IV.
  • Allison C4.
  • Ford M2C-138CJ.
  • General Motors Type A Suffix A.