Car preheating - when and how?
Published:
03.11.2025
Updated:
03.02.2026
In winter, pre-heating your car is one of those things that makes your daily life more comfortable while taking care of your car. When you heat your car before driving, the engine starts more smoothly, the interior is pleasant, and less fuel is consumed. Pre-heating should be started when the temperature drops below +5 degrees Celsius. As the frost tightens, the heating time should be extended: about 30 minutes at zero degrees, and about 1–2 hours in temperatures below -10 degrees Celsius. This article covers when and for how long to heat your car to get the most out of winter driving.
What is Car Pre-heating and Why is it Important in Winter?
Car pre-heating means heating the engine and the interior using electricity before setting off. An engine block heater keeps the engine oil and coolant warm, while the interior heater ensures comfortable driving and defrosts the windows. These functions are important in winter because a cold engine consumes more fuel, suffers from increased wear, and releases more harmful emissions into the air.
Pre-heating protects the car's mechanical parts because cold oil does not lubricate as effectively as warm oil. When the engine is pre-heated, it starts more easily and reaches its optimal operating temperature faster. Interior heating, in turn, improves visibility and safety, as the windows are not frozen and fogged up.
In Finnish winter conditions, pre-heating is practically a necessary comfort factor, but also a sensible way to extend the car's lifespan. When you know when and for how long to heat, you get the best benefit without unnecessary energy consumption.
When Should Car Pre-heating be Started?
Car pre-heating should be started when the temperature drops below +5 degrees Celsius. This is the limit where a cold engine start begins to consume more fuel and strain the engine. The colder it is, the more important pre-heating is for both driving comfort and the car's condition.
In practice, it is advisable to follow weather forecasts and start using pre-heating from late October onwards, as night frosts become more common. In late winter/early spring, when temperatures rise back above zero, pre-heating is no longer needed. If the temperature stays close to zero, you might consider pre-heating only in the mornings when the frost is strongest.
Do not heat the car unnecessarily. Electricity is wasted, and there is no significant benefit from pre-heating when the temperature is above +5 degrees Celsius. Timely pre-heating saves both energy and money, while the car's engine stays in better condition for longer.
How Long Should the Car be Heated Before Setting Off?
The car heating time depends on the outdoor temperature.
- In temperatures below +5 degrees and around zero, about 30 minutes is enough for the engine to warm up sufficiently and the interior to start defrosting.
- In frost around -10 degrees Celsius, heating for about an hour is recommended.
- In temperatures below -10 degrees Celsius, 1–2 hours is needed for the engine to be properly warm and the interior comfortable.
The heating times for the engine block heater and the interior heater can differ. The engine block heater usually needs a longer time because its job is to heat all the engine oil and coolant. The interior heater can run for a shorter time if you only want to defrost the windows and heat the cabin.
Overheating is a waste of energy. Unnecessary or overly long heating is not beneficial, and it consumes electricity needlessly. Heating for more than 3 hours is not recommended. The correct heating time saves money and is more environmentally friendly. You can use a timer to automate the heating to start just at the right time before departure.
Webasto – Flexible Non-Electric Heating
Webasto is a general term for fuel-operated auxiliary heaters that use the car's own fuel (petrol or diesel) to heat the engine coolant and the car's interior. Webasto is practical and enables pre-heating anywhere without an electrical connection – a luxury and ease for daily life!
- Operating principle: Webasto heats quickly and often heats the engine in addition to the interior temperature.
- Control: Via remote control, timer, or mobile application.
- Note: Webasto consumes fuel and also the car's battery. Heat with Webasto for about the same amount of time as you drive so that the battery has time to recharge. Additionally, it is good to use Webasto regularly year-round to keep it in working order.
What is the Difference Between Engine and Interior Pre-heating?
The engine block heater and the interior heater serve different purposes. The block heater heats the engine oil and coolant, which protects the engine from wear and reduces fuel consumption at startup. The interior heater, in turn, heats the car's interior and defrosts the windows, improving driving comfort and visibility.
There are differences in power consumption. A block heater typically consumes 400–800 watts, while an interior heater can consume 1000–2000 watts, depending on the model. Together, these can consume about 2–3 kilowatt-hours during two hours of heating, which is still less than the extra fuel consumption caused by a cold start.
You get the best results by using both together. Engine heating ensures the car's technical condition, while interior heating ensures comfort. By using both sensibly, you get a safe and comfortable start in all conditions.
How Does Car Pre-heating Affect Fuel Consumption and the Environment?
Optimized pre-heating significantly reduces fuel consumption. A cold engine can consume up to half more fuel during the starting phase because the oil is thicker and the engine does not operate efficiently. When you pre-heat the engine, it starts at the optimal temperature, and consumption remains normal from the beginning.
The environmental effects are also clear. A cold engine releases more harmful emissions into the air because the fuel does not burn completely. A pre-heated engine produces fewer emissions and runs cleaner. Furthermore, the engine wears less, which extends the car's lifespan and reduces the need for maintenance and repairs.
The cost of electricity is generally less than the extra fuel consumption. Although pre-heating costs a few cents per use, you save more in fuel and car maintenance in the long run. Pre-heating is therefore sensible both economically and environmentally.
Also Remember
- Electric Cars: Pre-heating is also recommended for electric cars. If possible, time the heating to occur while charging. This way, the heating does not deplete the car's battery, and the battery reaches a better operating temperature.
- Safety: Pre-heating ensures better visibility when the windows are not fogged or iced, which increases safety when setting off.
- Idling: The engine can be allowed to idle for a maximum of two minutes before driving, but in cold weather, a short idling time, up to four minutes, is allowed in temperatures below -15 degrees Celsius.