I got the in-dash non-Behr unit this summer, incombination with the stock
unit over the back seat. (This is the one plugged by Roadhaus Larry,
installed by the guy in Rockwall, Texas--don't have the link on this
computer.) He installed it with Freeze-12, which is mostly R-134a. This has
made all the difference for summer roadtrips; across Texas, from Fort Worth
to Branson, all without sweating. I have modified the rad. fan switch so it
blows all the time the AC is on--engine temps actually stay cooler than with
the AC (and fan) off.