Originally Posted By: martinq
Originally Posted By: G-MAN
You cannot "easily" make ATF+4 with Group II/III mix. Unlike typical OEM licensing requirements for an ATF, which are normally performance parameters where the oil manufacturer is left to create their own "formula" so long as it meets the performance spec, Chrysler's ATF+4 license stipulates the exact formula that must be used right down to the base oils.
I believe you are right about the base-oil requirement but I also think that the performance requirements of the (1998 spec) ATF+4 could easilly be met by a mix of currently available GroupII/III base (semi-synth). I don't doubt that every licensed ATF+4 being sold is currently using the required base-oil and add-pack.
When I look at this chart I'm reminded of how far behind the ATF+4 is compared to everyone else, but yes it looks like they require GroupIII in their licensed formula. I don't know if Chrysler is in any position to develop a new spec these days, they might just adopt one and put their stamp on it.
The whole notion that ATF+4 is an antiquated transmission fluid simply because it's a higher viscosity than these newer fluids is totally bogus. From a formulation standpoint, ATF+4 was light years ahead of its time when it came out and today remains one of the most advanced and shear-stable ATFs made. IMHO, other fluids, while going the LV route, are just now catching up to ATF+4 in terms of formulation.