Interesting info Don, thanks. I think my '97 Crown Vic is old enough for the "old green stuff" Like your F-250 it is old school, (why I have it) :) The only time I have seen 50/50 go to slush, and that IS a real thing, was 20 odd yrs ago when we saw -40 actual temp, my Dodge Omni miser edition started but the engine was so far from the fire wall it came to temp but the heater core lines were so far from the core they did not thaw out, engine was up to temp, I let it run for a half hour before leaving for work, but no heat in the cabin, thought I Iost a frost plug, it was the 2.5 feet long heater core hoses, took a hair dryer to them and it opened up, had great heat. let that car idle 9 hrs at work on my shift, burned about a half gallon of fuel, was toasty warm inside when i made my way home. $100 dollar beater. Drove it 3 yrs. 1.7litre VW 4cyl, only avail in the miser edition of the Omni. 4spd stick Bought it for 100 dollars and a battery. :) Had to buy it only had a motorcycle at the time and it was november...I think the cheap stuff will be fine in the Crown, if not I will eat my hat.