The part number for GM power steering fluid changed at some point from 1050017 to 89020661. Anybody know what has changed, if anything? The aftermarket fluids at the parts stores (Autozone, Advanced Auto Parts, O'Reilly) all reference the 1050017 part number and a GM Spec - GM9985010. Is there a new spec for 89020661? Is the new stuff the same color as the old stuff?
Part number 89020661 has now been replaced by 89021182. The description of the newer fluid is (from Amazon.com - same in other places):
Typically, when an auto manufacturer like GM supersedes an older part number, the newer part number will be compatible in place of the older version. I don't know what the older version's color was, but "amber-colored" seems pretty common for power steering fluid.
EDIT: Another, more innocuous reason, for changing a part number is they create a new contract with a different manufacturer. To identify the new "part" they put a new number on it. And along those lines, if the first part supplier goes out of business, GM would have to look for, and get a new supplier, and then again, put a new part number on the part.
Reading further on a website called Bob Is The Oil Guy, they have reference to what I have mentioned above. This suggests a couple of things, one of which states that the new fluid is actually provided to GM by a company called Gold Eagle. This is billed as a "universal" power steering fluid which can be mixed with other types of power steering fluid. Thing is, though, this is the same exact stuff GM is selling as PN 89021182. When I say the same exact, it appears Gold Eagle has a patent (or trademark) on the shape of the bottle. If you look at the GM bottle, it is that same shape, so don't doubt it is the same. Mind you, the Bob website is open to interpretation or input, but it seems viable and reliable in this case. One of the links on the Bob site, points to the Material Safety Data Sheet (MSDS) of this stuff. If you don't fall asleep reading it, it has a lot of information on the fluid itself, especially what it's made out of and additives and such.
You should be able to find the newer part number all over the place ... here is a Google Search on the part number. Hopefully this helps answer most of your questions.