Dex 6 Supersedes all of the other older Dexron fluids and is a much better synthetic fluid, able to handle higher temperatures, with better cleaning properties.
Here are some of the advantages of Dexron VI.
Extended fluid life,Improved oxidation and thermal stability
Optimized frictional properties that provide smooth gear shifting during low temperature operation and help prevent transmission vibration
Outstanding resistance against sludge and deposit formation
Improved anti-wear protection which contributes to extended transmission life
Outstanding low temperature performance. (much better in the cold it is synthetic)
I use Mobil 1 Dexron VI . There are many approved brands to choose from.