transmission fluids in a very very simplified explanation is this. Where the fall on the time line of being created means that are better than all previous (not 100%) fluids. Therefore if the LT71141 was created before the Pennzoil ATF, the pennsoil was able to meet those standards, and then dex6 came out, and was a standard higher than the pennsoil..

make sense? for the most part newer is better, but there are points where compatibility and transmission type matter. PLUS many companies ran different ATF in the same years, so its much much more complicated than i am saying..