"The Penny Test," as it's known, tests if your car's tires still have a deep enough tread to make them safe enough for winter driving (tread is what gives the tire traction).
In the US, tire tread depth should be 2/32" minimum. To check whether your tires need replacing, place a penny between the tread ribs with Lincoln's head pointing down into the tread. If his head is visible, it might be time for a new tire.
uhmm...no, it doesn't work like that
fan has not enough pull power to suck the colder air from floor level, you need to force warm air that is stored on ceiling level down so it mixes with the colder
that is much more efficient way of heating up large air volumes