They would, in theory. But you are adding complexity to the system, which is not a good thing.

I regard the car interior as the same thing as the interior of my winter tent. I don't need to heat the interior of the tent, why bother with that of the car? I simply need to keep that little sliver of air around my tender pink body at a comfortable temperature.

This is a pretty good situation for using MREs,along with their flameless heaters. I have never used one of these heaters, but I imagine they would take the sting off, once they have accomplished their task of preparing your hot meal, along with the indispensable nice cup of tea.