For what it's worth, I was in Home Depot yesterday and saw that they were selling their two windshield washer fluids for 69 cents a gallon.  I couldn't resist and bought up ten cases so far (60 gallons) of the higher test -30 degree stuff (orange like my tractor).  I couldn't get any more into my car but I intend to get another 40 gallons. so I'll have the 100 I need to load tires.
 
This price is about two bucks less per gallon than wintertime pricing.  I may even dilute the orange stuff a bit with water as I don't really need -30.