The half-tank habit

The single cheapest winter habit: never let the tank drop below half between November and March. It costs nothing, because you buy the same fuel either way, just a little sooner.

A jam burns more than you think

An idling engine with the heater on uses roughly a quarter to half a gallon an hour (1 to 2 litres), depending on the engine. A two-hour standstill on a closed bridge approach can take a real bite out of a quarter tank, and the detour afterwards is longer than your usual route.

Less air, less water

A near-empty tank holds more air, and on cold nights that air leaves condensation behind. A full tank and a bottle of gas-line antifreeze keep water out of the fuel line on the coldest mornings.

The pump likes it too

On most cars the fuel pump sits in the tank and is cooled by the fuel around it. Running low regularly works it harder.

Driving electric?

The same rule, with a twist: cold cuts range, sometimes by a third. Keep the charge above half, warm the cabin while the car is still plugged in, and use the seat heater before the cabin heater when you're waiting.

Make it automatic

Pick a trigger you already have: fill up whenever the gauge touches half, or every time a storm shows up in the forecast. Either one beats remembering.