all levity aside, the fact that that chart says that the operational allowance for antifreeze is from 7-11 pH means, almost explicitly, that the pH doesn't matter. pH only goes up to 14. i'd bet that you could subtract the pKa from 7 and be safe down to a pH of 3 and not damage your cooling system (you might have some weird reactions with plastics, but you'd have the same reactions with plastics if you let the ph go up to 11). pH is a logarithmic scale, 4 is a big difference in a place where electrolysis and deposition and owners adding tap water can go on unchecked. if they were going to say that typical operational ph would be up to 9.5, i'd buy that it mattered. i would almost wager a bet that your indy uses the pH as only a small part of the puzzle, that they wouldn't dump the stuff out if it were 11, but they would dump it if they saw rust in it. specing an antifreeze with PO4 for ph buffering (american green) without PO4 buffering (euro/bmw/merc) and then
1) expecting the owner to never put tapwater in the radiator, ever
2) making a perfect 50/50 or 60/40 mixture of antifreeze in bmw's labyrinthe
cooling system
3) (and this is important) making sure that the "distilled" water is exactly 7 ph (utterly laughable)
and then using these criteria to establish a standard for operational PH in your car is unbelievable. none of the university of florida DI plants can produce exactly 7.0 ph deionized water, you have to use buffers with your experiments. they have a great deal to gain by giving their labs clean water, but they can't do it. marine fish shops can't do it, i'd bet your indy's di'er or filter setup can't do it (if they have one), and even if they fill your cars with jugs of distilled from the store, they can't provide it. the second you put anything other than ph 7.0 water into the antifreeze (which is what they used to produce the document bill posted), you vary wildly from spec. add in the nastiness from your motor, and you better believe that that ph is not representative of any kind of dealbreaking standard for antifreeze pH. saying that ph matters when the document specs a ph range of 4 is like me running a conductivity test on my used motor oil to determine fuel dilution. the result may say something, but it isn't saying much.
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