Do You Really Need to Warm Up Your Car in Winter?

On a freezing morning, many drivers start the engine and go back inside for ten minutes.

It feels like the right thing to do for the car.

For most modern vehicles, though, a long warm-up is a habit from another era.

This guide explains what official fuel economy research says about warming up your car in winter.

It also covers why your gas mileage drops in the cold and what you can do about it.

The short answer: about 30 seconds, then drive gently

According to FuelEconomy.gov, most manufacturers recommend driving off gently after about 30 seconds.

The site is run for the US Department of Energy and the Environmental Protection Agency.

It explains that the engine warms up faster while it is being driven.

That means the heater starts working sooner, too.

Driving off gently also decreases your fuel costs and reduces emissions.

The key word is gently. For the first few minutes, avoid hard acceleration and high engine speeds.

Your owner's manual is the final word for your specific vehicle, so check what it recommends.

Why idling to warm up wastes fuel

A car that sits in the driveway with the engine running is burning fuel and going nowhere.

FuelEconomy.gov puts it bluntly: idling gets 0 miles per gallon.

Its driving habits page adds that idling can use a quarter to a half gallon of fuel per hour.

The exact amount depends on engine size and whether the air conditioner is running.

Here is a simple way to picture it.

At a quarter to a half gallon per hour, a ten-minute warm-up burns roughly 0.04 to 0.08 gallons.

Repeat that on 100 cold mornings and you have used about 4 to 8 gallons while parked.

What about remote starters?

Remote starters are popular in cold states because the cabin feels warm when you get in.

From a fuel point of view, though, a remote start is still idling.

Every minute the engine runs in the driveway uses fuel without moving the car.

If you use one, keep the run time short and start driving gently once the windows are clear.

In an electric vehicle, the better option is to preheat while the car is plugged in.

Why your car gets worse mileage in winter

Even without long warm-ups, winter is hard on fuel economy.

FuelEconomy.gov reports that a gasoline car's city mileage is roughly 15% lower at 20°F than at 77°F.

On short trips of 3 to 4 miles, it can drop as much as 24%.

Hybrids are hit harder, with drops of about 30% to 34% under the same conditions.

Several things work against you at once.

  • Thicker fluids. Cold engine oil and other drive-line fluids increase friction in the engine and transmission.
  • A slow warm-up. The engine takes longer to reach its most efficient temperature, which hurts short trips the most.
  • Extra power use. Heated seats, window defrosters and heater fans all draw additional power.
  • Denser air. Cold air increases aerodynamic drag, especially at highway speeds.
  • Lower tire pressure. Tires lose pressure in the cold, which increases rolling resistance.
  • Winter gasoline. Winter blends can have slightly less energy per gallon than summer blends.
  • A weaker battery. Battery performance drops in the cold, so the alternator has a harder time keeping it charged.

Snow and ice make things worse.

Slick roads reduce tire grip and force lower speeds, and four-wheel drive uses more fuel.

Smarter ways to warm up the car

You cannot change the weather, but a few habits help the car warm up faster and use less fuel.

Park in a warmer place

FuelEconomy.gov suggests parking in a warmer place, such as your garage.

A car that starts warmer reaches its efficient temperature sooner, and the cabin heats up faster too.

Combine your errands

Short trips with a cold engine are the least efficient kind of driving.

Combining several errands into one outing means fewer cold starts and more miles with a warm engine.

Clear the car before you go

The National Weather Service says to make sure your vehicle is completely clear of ice and snow before a trip.

Brush off the roof, hood, lights, mirrors and every window.

If the glass is frozen, use the defroster until you can see clearly.

Safe visibility always comes first, even if it costs a little fuel.

Use the extras wisely

FuelEconomy.gov advises not to use seat warmers or defrosters more than necessary.

Never drive with fogged or icy windows to save fuel, though.

Turn the extras down once the cabin is comfortable and the glass is clear.

Car care that helps in cold weather

A few maintenance checks make a real difference once temperatures drop.

  • Check tire pressure regularly. Pressure falls as the air gets colder. Our guide on how to check tire pressure shows the right way.
  • Use the right oil. Use the type of oil your manufacturer recommends for cold weather driving.
  • Remove roof racks you are not using. They increase wind resistance on every trip.
  • Get the car ready early. Our guide on getting your car ready for winter covers fluids, battery, wipers and an emergency kit.

If you drive a hybrid or an electric vehicle

Electrified vehicles feel the cold even more.

FuelEconomy.gov reports that an electric vehicle's range can drop by 41% in cold weather.

About two-thirds of the extra energy goes to heating the cabin.

Two habits help.

  • Preheat while plugged in. Warming the cabin while the car is still on the charger can extend your range.
  • Use the seat warmers. Heating your seat instead of the whole cabin can save energy and extend range.

A quick cold-morning routine

  • Clear all snow and ice from the windows, lights, roof and hood.
  • Start the engine and wait about 30 seconds, or what your manual recommends.
  • Drive off gently and avoid hard acceleration for the first few minutes.
  • Use the defroster as needed to keep your view clear.
  • Group errands together so the engine stays warm between stops.

For tips once you are on slick roads, read our guide on driving on snow and ice.

The bottom line

Long warm-ups are mostly a waste of fuel and time.

A modern car warms up faster on the road, as long as you drive gently at first.

Clear the car, give it about 30 seconds and go.

Pair that habit with good tire pressure and the right oil, and winter will cost you a little less.

Sources and Further Reading