My late father said way back during his welding days that some of his coworkers would warm up their lunch pails that way. It helped that those Malaise-era vehicles had really low thermal efficiencies, so all they had to do was idle for 10 minutes while they washed all the soot off themselves.
OH MY GOD, THE FRONT WINDOW IS STILL MISSING AFTER NICK SMASHED IT FOR BEING FROZEN OVER!! Oh that is the funniest shit. Out of all the details in this manga so far, none made me laugh as hard as this one.