I've been watching 'Ice Road Trucker' on TV and they use some kind of fluid to dry out air lines when things are really bad. Can't remember what it is but it is mainly ethanol, or methanol. Can't remember which. Those systems have to take care of the trailer air brake system too, though.

195? Chevy 3800 dump truck
1973 Chevy C30 cab and chassis
1987 Suburban 3/4 ton 6.2L Diesel