for most places where it REALLY gets cold, the evaporators are the weapon of choice. some folks forget alcohol / methanol mix with water and settles to the bottom of the tank eventually. that way, every time the brakes are applied or air operated windhield wiper, or control are operated, alcohol vapor is in the air. evap's are not affected by any oil that gets into the system either, and actually help the oil settle to the bottom of the tank.
i had a drier on both of my road tractors, but installed evaporator as well for those northern canada runs in the winter. i never had a freeze up problem. when i was a shop foreman for a local trucking company, we installed evaoprators on 181 trucks after a series of bendix driers failed during the winter. by the time 3 years had gone by, nearly every truck had the driers by-passed due to failures. we didn't bother to replace them. probably the newer generation of driers is better, but i have no experiance with them. i sure didn't care much for the old "dome top" bendix, with a 50% failure rate in 3 years. we also ran our trucks almost constantly too, and i suppose that is also a factor.
