I need to do a automatic transmission fluid change on a 2005 GMC Jimmy. The manual specifies DEXIII "Approved for the H-Specification". What is the "H-Specification"?? I'm assuming this is now compatible to DEXVI correct? Would this truck be a good candidate for Valvoline Maxlife Dex/Merc ATF? It has about 155,000KM on it and has never had an ATF fluid change done. I recently flushed my 2003 Montana with maxlife and had great results!