Transmax Dex VI - Automatic Transmission Fluid. Castrol Transmax Dex VI is approved for use in all General Motors automatic transmissions. It is licensed against Dexron® VI which supersedes all previous Dexron® specifications for General Motors Holden applications.;Advantages;Low viscosity formulation provides fuel economy benefits compared with fluids formulated to meet Dexron® IIIH or earlier specifications.;Premium synthetic formulation gives outstanding oxidative resistance extending transmission life.;Enhanced friction durability improves shifting performance.