I changed the fluid on my wife's HHR with 4T40E at 140k and what came out looked like what went in. This trans is spec'd for Dex VI as of 2007 but took the cheap stuff earlier, and There's substantial torque management from the electric throttle which helps it rev-match mid-shift. Very smooth and easy on the trans. I would not be surprised to see these things last a lifetime on original fluid. Lifetime being until the ecotec lets go.