This testing was done, first, to evaluate the effects of mixing "old" and "new"
antifreezes observing the effects of temperature change. Tested was a new Prestone 
"all use" mixture versus a (very old) Zerex mixture as well as a 50/50 mixture of
the two. See notes at link below.
Secondly, an electrolysis test was performed on the same mixes to assess what
might happen if there is a voltage potential difference between an automobile
radiator and the engine.  Used (both at a ~50% mixture with faucet water) were:
	Prestone "Extended Life Antifreeze/Coolant
	Zerex "Antifreeze Coolant For Extreme Conditions"
	A 50/50 mix of the Prestone & Zerex products.
	Aluminum strips and pieces, about 0.007 inches thick (building flashing)
In the boil/freeze test, aluminum pieces about an inch square were placed in
the solutions. The solutions were then alternately frozen, returned to room
temperature, then boiled and the cycle repeated for several days. This work
provided little information as none of the mixes showed any degradation either
in terms of metallic corrosion or coagulation. It is worthy of note that the
Zerex solutions would not readily strain through a standard coffee filter while
the pure Prestone mix would.
In the electrolysis test, aluminum strip electrodes were placed in the solutions.
Voltage was applied to the strips from a 12 volt battery. The test was suspended 
after 12 hours for the pure Zerex mixture as significant corrosive damage was noted. 
The Prestone solution testing was stopped after 24 hours as no electrolysis 
activity had been noted (no bubbling at the electrodes).
The electrolysis test for the mixture of Prestone and Zerex had an interesting
result. As with the Zerex only solution, electrolysis activity started in seconds.
Differently, though, it seemed to stop after a few hours and appeared non-existent
at the conclusion of 24 hours. However, there was significant debris build up
on the positive electrode as witnessed in the pictures. There was little apparent
damage to the metal of the electrode, quite different than the pure Zerex
solution test. Clearly the addition of the Prestone mitigated the corrosive
damage.
Result pictures show detail of the electrodes (aluminum strips) and the Zerex
solution following the test and then the residual debris in the three solutions
following straining through a coffee filter after the test.
Similarly, the pictures show the residual from straining the mixtures after 
the boil/freeze testing. Basically, nothing noticable either in terms of debris
or damage to the aluminum pieces.