I'm not arguing Scott, but isn't it also possible that Optimum relabled his product for Prestone? He would then be selling his patented product to them, and not sharing what his ingredients are with anyone.
Markthom stated there were more similarities than just the packaging, such as the scent, etc. I'm not saying he's right, and I'm agreeing that similar packaging is inconclusive (to the point of by itself being insignificant), I'm just saying that it's possible that Optimum made the stuff for Prestone, just as they may have made "SunX".
I wasted a bunch of time today trying to hunt some of this stuff down (prolly would have been cheaper to buy some OCW!), and since it seems to have been discontinued (can't find it on the Prestone website), I'm thinking the place to find it is a small auto parts store, since any of the chains would have cleared it out.