I tried cooking bacon in the car on Monday, July 2. I had a doctor's appointment that morning and so I didn't get to work until about 9:15. I placed the bacon in a small baking dish and placed it on the dash before heading in to the building.
I got off work around 4:00 that day and while it reached over 100 degrees during the day, it was also overcast on and off throughout the day so I'm not sure the bacon got the full Cooking in the Car effect and I would like to try it again maybe with a drip pan. I will say the car smelled like bacon and you can't go wrong as far as that is concerned.
There was A LOT of grease in the bottom of the pan and the edges of the bacon had cooked, but it had by no means cooked all the way through. Perhaps on anther hot and sunny day, the bacon might cooke a little better.
So, if you want bacon, it's probably best to just go ahead and cook it on the stove, or the oven, or whatever your normal method of cooking is.