Hi MCIbus,
You have the right idea--but it is backwards. Butane has a higher boiling point than propane (-1 C for butane, and -42 C for propane). In the south--it doesn't matter and butane actually has more "heat content" than propane. Where it is cold it does matter.
MCIbus wrote:
The only thing I could think of dose not sound right from the information that was given.
During the winter the propane tank got to cold and the liquid would not be able to evaporate at the speed that was needed, but this happens at high flows. During the winter butane is often mixed with propane and keeps the tanks from “freezing up”.