I'm not an expert and I have no scientific knowledge about rate of burn on an idling engine. But here is what I actually experienced with 3 different MB diesels at idle using only Diesel Purge to clean the injectors .
Car 1: 1984 240D: one pint of Diesel Purge: Yes I know this is not diesel fuel, and yes I know it is not the same car as was in the thread. but it used up the pint in about 15 or 20 minutes to the best of my recollection.
Car 2: 1976 300D, I put two cans of Diesel purge in a bottle and drove the car around a little and probably ran it for about 20 minutes or so.
1984 300D TurboDiesel: Ran one can through blasting around the neighborhood and I believe it lasted about 15 minutes or so.
Sorry I don't have exact figures, and I also guess that there is a lot less energy per pound in the Diesel purge vs pump Diesel fuel.

Running the car overnight is probably ok for an emergency, but I would imagine the more sensible and more economical thing to do, and more engine preserving thing to do, and less polluting thing to do, (did I get enough of the to do's?) would be to install an engine block heater, cover the engine with a blanket and leave one corner of the blanket sticking out from the hood by the driver's side windshield wiper as a visual clue NOT TO START the engine until you remove the blanket. Use Cold flow fuel additive as well. Hope this helps.
Rich