Golly, you hit a spot for sure, this thread grew fast!!!
I think we should start a collection and bring Daisy and Delilah's mom up here for a week right now so she can experience all the fun first hand!!
The serious reason for keeping the gas tank full has been mentioned, to avoid condensation. But another reason is that, if the cover to your gas cap freezes, then you can't ADD any gas until it thaws! And yes, the doors may freeze shut, especially on the side getting hit with the wind. Many times I've only been able to open the passenger side and had to climb over to the driver's seat. Not too easy with bucket seats and the shift on the floor there!
There is stuff you can add to your gas line to help prevent freezing and condensation. And of course antifreeze in the radiator is a must. You better make sure you are using the right window washer or your wipers will freeze to your windshield and you will have a sheet of ice on there. For years Dad took his car in every Spring and every Autumn. Autumn was to winterize the car, have all the warm weather stuff drained out and the cold weather stuff put in. We use a different oil in the car in the cold weather, than in the summer, too. Then in Spring, all that had to be drained and the warm weather version put in.
I used to enjoy winter, when I was younger. I was into sledding, toboganning, and skiing. Now I can't do any of that stuff and I do not enjoy winter as much. I do find I plan my trips, based on the weather. Today for example I did NOT go out, and Sugar did NOT get her 30 minute walk. She was just in the backyard a bunch of times to stretch her legs.
When I worked in a professional office setting, it was common for women to keep "work shoes" in their desk drawer. You come in to work and shed all the outer garb, the boots and multi pairs of socks, and put on your "professional" look. Many women spent time in the ladies room adjusting their hair, and I mean TIME, with blow dryers and curling irons and all. Makeup is GREAT to protect your skin in the cold, so women always came in with that already on. Some of us even wore our glasses to commute and switched to contact lenses after we arrived. Since the cold wind can make your eyes water, that is not a good way to keep your contacts in. Many of the men where I was working came in and shaved after they arrived. Didn't like the cold on the just shaven skin.
I grew up in Massachusetts; in my 30's I lived in Maine for 5 years. I thought I knew what winter was. HA! Their snow plows for clearing the roads are humongous! My last winter there, we had a total of 127 inches of snow. That was it, I said "I'm outta here before another flake hits the ground!"
If you grew up in cold weather climes, you grew up seeming to "KNOW" all these things, it is interesting reading this thread and realizing how much we do "naturally."