Russell,

There are two products that I know of that provide 1) pump & seal
lubrication/protection and 2) corrosion protection:
   "Water Wetter" -  Motor cycle shops have it - expensive.
   "John Deere Coolant Conditioner" - cheaper and does same thing - lubs &
protects.  I talked to the Deere engineer for 30' on the phone and he says
it should work fine.

Either of the above will give the same protection as antifreeze but with the
superior heat carrying capacity of pure water.  I'm planning on running this
stuff  (water with conditioner) during times when freezing level is up above
10 or 12 thousand feet (it's 15K here in Texas in summer), then swap out to
50/50 when cooler OAT and therefore don't need "optimum" cooling.

David