Yup, I have several bags of charcoal for the barbecue, and sometimes I need to park vehicles where they can not be plugged in.

If I could stuff your can stove with charcoal, light it and put the lid on it, then it might be fine for thawing out a cold engine.
It could be prepacked and ready to light.

Just so long as it does not get too hot.
More like one of those handwarmers where you light the charcoal stick and close it.
Yup, like a large size handwarmer for my truck's motor.
Shove it under the oil pan and hopefully an hour later vroom, vroom, vroom.

I must build one and test it out.
I really don't want to be setting my truck on fire if your little stove turns out to be a raging inferno.