I am getting ready to have both of my cars ATF changed. 1993 Ford Explorer and 2001 Suburban. I have always taken my Ford to the same shop and they use Pennzoil. 1. Is there really any difference in ATF's that are made to each of the respective GM or Ford spec's? 2. Do any of the OEM's ATF have any extra ingredients in them that you don't find in aftermarket ATFs? I know that GM is supposed to have a special EP additive in their differential fluid that you don't find in Mobil 1 or other aftermarket diff fluids. 3. Is there any benefit to the new high milage ATF's like Maxlife, and others for my '93 Ford with 105K? So, Which ATF is better to use for my vehicles.