Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Antifreeze pH

In draining and changing my antifreeze I found a recommendation in an auto repair manual that antifreeze pH should be between 9.5 and 10. If pH is below 8 it said it should be changed. I ran a pH test on new clean Prestone antifreeze and found it to be 8.8. It appears that Prestone antifreeze is not capable of attaining a mixture pH of 9.5. In contrast a sample of Car and Driver pure antifreeze has a pH of 10.1. My question is this is pH something to be concerned about or is just attaining a new clean 50/50 mix and temperature protection to -40 degrees F good enough?

Modern antifreeze contains chemicals that maintain and adjust pH automatically. pH 7.6 is neutral. 10 is very alkaline, almost caustic…Cooling systems like to be kept a little base…Acid (pH below 7.2) is the kiss of death…

Actually, a pH of 7.0 is neutral. Anything higher is alkaline; anything lower is acidic. I would not worry about a pH of 8.8. Your Jeep may have an aluminum radiator and other aluminum engine parts. Aluminum is attacked by both alkaline and acid solutions. Going too far in either direction is bad. BTW, is the Prestone antifreeze you bought approved (by Chrysler) for your Liberty? Your owner’s manual may give you basic information about acceptable antifreezes. Also, what repair manual are you reading, and is it specifically for your Jeep?