Although not a scientific answer, I have mixed Mopar and generic P/S fluid with no apparent problems over about 30,000 miles. I will say though, that the pump and rack were already worn(noise & poor wheel return) prior to adding it(generic), so I knew I would be replacing parts soon.
Mopar now specs ATF+4 fluid for it's P/S systems. The design of the components appears to be the SAME, so this leads me to believe that the ATF+4 is an improvement and could/should be used in older systems that call for Mopar P/S fluid. For example, my 97' LHS calls for Mopar P/S fluid, but, the 00' shop manual(I use the 00' s/m because the price was right) says: use "only ATF+4"; both years use the same pump and rack & pinion(different part #'s though, the mounting holes are slightly different).
FWIW
I've since installed a new rack and pump; I'm shooting for maximum life, so I'm trying Amsoil universal ATF, which carries the ATF+4 rating.
Mopar now specs ATF+4 fluid for it's P/S systems. The design of the components appears to be the SAME, so this leads me to believe that the ATF+4 is an improvement and could/should be used in older systems that call for Mopar P/S fluid. For example, my 97' LHS calls for Mopar P/S fluid, but, the 00' shop manual(I use the 00' s/m because the price was right) says: use "only ATF+4"; both years use the same pump and rack & pinion(different part #'s though, the mounting holes are slightly different).
FWIW
I've since installed a new rack and pump; I'm shooting for maximum life, so I'm trying Amsoil universal ATF, which carries the ATF+4 rating.