How much heat will it really put out? I just received one as a gift and am wondering how much it would heat the cab of a car or a 2/3 man tent. I do carry a couple single wick beeswax candles, butI have always been a bit leery of open flames in enclosed areas. I do think this will make its way into my car kit if it is effective. Thanks!

This is a timely post, with motorists found deceased and one lady surviving 4 days nearly buried in snow.
I am not aware of any empirical tests. But anecdotaly I can tell you a snowcave with one or two pink lady type candles will reach a balmy 30 degrees. Before you shiver like I am doing ( explanation follows) remember that is with ouside temps dropping to sub zero readings.
In plain words, you will wake up in the morning, always a good product endorsement.Remember though, most vehicles are poor insulators and you need to improve your interior; small is beautifull like so many survival startegies.A sleeping bag, blankets, even a good thick sunday paper under the seat will vastly 'warm things up.'and if you have food ( my car has several meals in spilled popcorn, gummy worms and a few cherry slurpies I haven't cleaned out yet ) you can easilly fix it up by crumpling the paper for added insulation and feeding your inner furnace, or 'the Fire within' as this religious tract proclaimed in my doorhandle yesterday.
You will want at least one point of ventilation, even without a oxygen burning heat source, you alone can use up a considerable amount of fresh air in a sealed car,and that small opening may also serve to help hear nearby searchers.
Nuwick has a good product reputation. You own a winner.
Oh, I'm inside my wiggy bag drinking hot coffee. My cat Piewacket somehow exercised his territorial imperative for the first time in 3 years. He managed to nail the pilot light on my gas furnace (He gets his keen marksmanship from my side of the family), and I can't get it to relight, had to shut the valve closed and have my oven cranking out a little added warmth.

Here's what I can tell you - recently we were hitting temps in the low -30's here with windchill factors well into the -40's.
My father-in-law lives out of the city and broke down on the highway one night. We headed out to help him as soon as we got his call. Bought some coffee's on the way out at a Tim Hortons and arrived within 30 minutes to where he was stopped.
I tell you, in the open with that wind.. he was damn near frozen. A couple candles may have at the very least helped keep the chill off inside that vehicle until we showed up.
Since then I have rechecked our own vehicle kit and added a couple more candles just in case.

Yes they work well enough. If we are both talking about the ones that come in a tin like for shoe polish.
Two of those will warm up a small delivery van,(personal testing) just remember to have at least one window open a little bit.
As with all gear, try it out before you really need it.
Just dont put it on the dashboard because you will make the windshield dirty and you might crack the glass from heating it too much in one spot (personal testing results). (In most cars the glove box door seems like a good spot to set it to me).
They are refillable too, all craft stores seem to carry beeswax and wicks.

Another thing that works are those little candle lanterns they sell to the backpackers. The flame is a little bit protected and they usually just go out if knocked over.

Every degree you can raise the temperature inside your shelter adds to the chances you will survive. You will not be comfortable.