Several reasons are responsible for the fact that fuel consumption increases in winter. The most important of these are:

• Use of winter tyres
• Longer cold running phase of the engine
• More electrical consumers in use

1. Winter tyres
Winter tyres are usually made of a softer rubber compound and are inflated with a lower air pressure. This gives them a larger contact area on the road. In addition, the specific tread pattern ensures that the tyres adhere better to the road in snow and slippery conditions. As a result, the driver retains control of the car longer even in difficult weather and road conditions. The disadvantage, however, is the increased rolling resistance. This is one of the factors that increases fuel consumption in winter. To counteract this somewhat, the ADAC and some tyre manufacturers recommend increasing the air pressure by 0.2 bar. However, do not exceed the value so that enough adhesion remains. Because the more snow and ice there is on the roads, the more contact surface is needed for the tyres. As a further alternative to saving fuel, it is worth changing to energy-saving tyres. These can save up to 0.5l per 100 kilometres of fuel.

3. Many additional electrical consumers
The colder the temperatures, the more consumers are switched on in the car. This begins with the heating, continues through the ventilation and windshield wipers and extends to the fog lights. Then there is the running radio, seat heating, etc. All this additionally increases the fuel consumption of the car. The highest consumptions have all devices that have to do with heat. At the top are the following devices:

• the windscreen heating with over 500 watts
• the rear window heating (185 Watt)
• the ventilation (171 Watt)
• the seat heating (102 Watt)

The steering wheel heating (50 Watt) and the heated exterior mirrors (30-40 Watt) consume the least. The fog light (110 Watt) needs more power than the rear fog light (53 Watt). The windscreen wipers at the front (80-140 watts) and rear (30-55 watts) and the radio (20 watts) are among the least power-hungry. Per 100 watts there is 0.1l additional consumption per 100km. Therefore the rule in winter is: only switch on what is really needed and switch it off again as soon as possible when it is no longer needed! This means that the radio, as well as the seat heating and fog lights should remain switched off when starting, so that the engine can warm up faster.

As in summer, the right driving style is important here. Early upshifting, fast acceleration and a constant speed at lower revs help to reduce the fuel consumption of the car. In the warm-up phase you should drive continuously in the medium speed range. Constant acceleration and deceleration or short-term revving up of the engine, on the other hand, reduce efficiency and thus help to save fuel less.

It is also recommended to use the engine brake when driving in a fuel tank. This means that it makes more sense to slow down at the red lights and slow down towards the intersection than to brake hard just before. The same applies when braking down at town entrances. In addition, the engine should not be running at idle speed. When waiting longer than 20 seconds, the engine should be switched off if it has warmed up. This is even mandatory at level crossings. Nowadays, automatic start-stop systems control this themselves. They also only switch off the engine when it is warm enough. The additional load on the starter and the battery is not worth mentioning.

Another point that applies all year round is open windows and sliding roofs. These only have a consumption advantage over air conditioning in city traffic. At higher speeds, they cause the air flow to stall, which also leads to increased fuel consumption of the car. If you still want to open the window a little at higher speeds, you can use wind deflectors. These prevent the airflow from being stalled as much.