In the cold weather and winter it's best to always have a full tank of gas or at least near full tank of gas to prevent the car from running out of gas.
Also keeping your cars gas tank full or near full helps prevent moisture from collecting in the fuel tank which can cause problems.
To stop a car engine from freezing in the winter you'll need to put Anti Freeze/Coolant in the cars radiator.
If you're using water you need to drain out the water and add mixed Antifreeze and coolant to the car which prevents the cars engine block from freezing.
Antifreeze/coolant keeps your engine cool in warm weather and keeps it from freezing up in the winter.
A 50-50 mix of full strength coolant and water generally protects to around -30 degrees Fahrenheit.
Make sure you check with the supplier or your owner's manual for the correct formulation.
Sleeping in a car is not colder than a tent.
In fact sleeping in a car is warmer than sleeping in a tent.
The car is insulated and you can also use the engines heat to keep you warm.
The tent while better than no shelter is not insulated and you'll be much colder sleeping in the tent than you would in the car or other vehicle.
You can sleep in a car below freezing although you should have plenty of blankets and some heat source to help you stay warm.
Using tea candles safely can help add some heat and using thick blankets can help you keep warm.
Also sleeping with your head under the blankets is a good way to stay warm and you can use your breath to keep your warm as well.
Starting the engine and running the heater every hour or so for 30 minutes or so to heat the car up is also a good idea.
But you should not go to sleep with the engine running.
Homeless people keep cars warm by using candles such as tea candles.
The tea candles and candles when used safely can keep a car warm enough to allow you to survive.
Also homeless people will run their car engines and heaters for a while to warm the car up.
Homeless people also use lots of blankets, coats etc to keep them warm in the car.
A candle in your car can and will keep you from freezing as the candle produces a good deal of heat and can be used to keep the inside of the car warm.
However you must be careful when burning a candle inside the car and burn the candle inside a metal coffee can or pan and open a window slightly.
You can sleep in a car with the heater on if you need too but you must make sure the exhaust pipe is in good shape and make sure the exhaust pipe is clear to prevent carbon monoxide from building up.
Also keep a window slightly open a crack to allow some fresh air into the car.
However you should really just heat the car up for awhile and then turn the engine off for safety.
Cars lose most of their heat through their windows.
Trap warmth by putting a thick reflective sun shield in your front windshield, and cutting insets out of Reflectix wrap (available at most hardware stores) for your other windows.
Push the insets into the windows before getting ready for bed.
To prepare your house for extreme cold weather ensure your furnace is working properly, seal up any windows with caulking, cover the windows with plastic and seal off any holes or crevices that can allow cold air to enter.
Also install insulating curtains to help keep the cold weather out.
During cold weather keep faucets dripping to help prevent frozen water pipes and install insulation over the exposed water pipes.
Cover any outdoor spigots and remove any garden hoses.
To keep your house warm in the winter without electricity you can use your gas or propane stove if you have one.
The stove can be lit with matches or a cig lighter or use a Kerosene or propane heater that requires no electricity.
If you have a wood burning stove then that would be a good way to keep your house warm in the winter without electricity as well.
Also open curtains and blinds to allow plenty of sunlight in and keep moving.
If your house is too cold then consider getting into your car or vehicle and even sitting in it in your driveway as the sunlight can heat up the vehicle.
Or drive around town with the heater on until the power comes back on.
Also use more blankets than normal to stay warm.
To keep warm during a power outage you can use a portable generator to provide electricity to power an electric space heater.
If you have a gas stove you can use the gas stove for heat during the power outage or even the oven but you must be careful to avoid carbon monoxide buildup.
Another option is to cover your body with plenty of blankets and you use your breath for heat.
Also if you don't have a wood stove then that would be a good option to use in the event of a power outage.
Or install a gas or propane heater that requires no electricity.
Candles can also give off some heat.
During a power outage it's always a good thing to have a backup source of heat to heat your home because when the power goes out your furnace with the blower will not work.
A natural gas wall heater that is vented is a good idea or even those natural gas vent free heaters are good for use in emergencies and they don't require electricity to run.
A wood stove is another option or a coal stove that doesn't require power.
If you have no other form of emergency heat then you need to layer in blankets and bundle up really good to keep in your body heat.
If you have to sleep in the cold in your house then layer on lots of blankets and wear a coat to bed as well.
Cover your whole body and entire head with the blankets because the breath you're breathing will be warm and will warm you up under the covers nicely.
I've done that before and I survived a freezing cold house for 2 weeks until the power got restored after an ice storm.
A portable propane buddy heater can also keep you warm or even a torpedo heater but be aware of carbon monoxide poisoning.
When a power outage may occur such as an oncoming ice storm be sure to turn your thermostat up so the furnace will run longer and heat your home to a warmer temperature.
This will help keep your house warm for a little longer after the power goes out.