I think a Dietz lantern would work quite well. Certainly safer than an open pot of liquid fuel. I have several, and even used 2-3 of them one year to protect my tomatoes from a surprise frost. They put out a surprising amount of heat.

In my part of the world, liquid paraffin is a tricky proposition. It's less smelly, true, which would be more pleasant in a vehicle; but it also turns into a semi-solid as the temperature drops, which would be a major problem. Kerosene doesn't have this problem.

Hmm, outside my window it's -12C with a howling wind and blowing snow (semi-whiteout conditions), and a wind chill of -22C. And I have an old car parked in the middle of my yard, half buried in the snow, and I could just throw in a thermometer and do some field tests with candles and lanterns ...