To build on Neil's point...
A propane-fueled vehicle normally withdraws the propane
from the tank as a liquid (which means the tank doesn't need to be supplied with the heat to vapourize the liquid propane), and converts it to gas in a vapourizer, which in turn gets its heat from engine coolant (which means the part which reduces the pressure doesn't risk freeze-up).
Even with liquid withdrawal the vehicle tank should still cool somewhat, because as the liquid is taken out some of the remainder must vapourize to fill the space, but this is only a small fraction of the propane
(in the end, just one times the tank volume), so it doesn't need to absorb heat from the surrounding air at nearly the rate (per pound of propane
used) as the tanks for our vapour-fueled RV appliances.