On an interesting side note the guy at MR LUBE said that you definitely can control the PH by changing the ratio, adding more water will get a lower PH, adding more coolant will get a higher PH. He mentioned that in his personal experience it makes a big difference where the water comes from. And that water (even distilled) varies greatly and often isbelow the normal water PH of 7. I will go back tomorrow and re-test (after the concentrate has had a chance to mix from the overflow bottle).