Does A Sunroof Increase Drag? Open And Closed?

Many things can slow your car down and reduce your fuel efficiency. Does a sunroof increase drag?

I often drive with my sunroof open even though it creates a bit of drag. I have a wind deflector so it doesn’t reduce my car’s performance or handling very much. 

An open sunroof disrupts the airflow and makes it take more energy to maintain the same speed. 

Does it Impact Performance? 

It sometimes makes enough of a difference that your car’s performance noticeably suffers. You’ll still go fast, but you won’t accelerate as fast and you will get worse gas mileage. 

How Drag Works

Drag affects all vehicles and all moving objects. Runners experience drag, a baseball experiences drag, and bicycle riders do. Whenever any object moves through the air, the air pushes back on it and slows it down.

There is also drag for anything moving through water, which pushes back harder than air and makes it hard for a boat to travel very fast. Many things are designed to reduce drag, from airplanes to golf balls. 

If two cars have the same engines, the one that cuts through the air better will go faster. Less drag also means more fuel efficiency. 

Driving Faster Uses More Fuel Per Mile

Anything above around 45mph makes your car less fuel efficient. Drag increases and your car has to work harder to maintain the same speed. 

This gets more and more true at higher speeds. At 80mph, you will use 28% more fuel than at 55mph. 

How an Open Sunroof Significantly Increases Drag

If you drive with an open sunroof and no wind deflector this may cause wind buffeting. Wind buffeting may make it hard to control your car. 

Fast-moving air from the outside will interact with slow-moving air inside the vehicle. This makes the air compress and decompress over and over. Even opening a window may cause some wind buffeting at high speeds. 

Wind buffeting is noisy, makes your engine have to work harder, and can even be dangerous. Wind buffeting from windows is often worse with newer cars. However, newer cars have wind deflectors for their sunroofs. 

Opening Multiple Windows Can Help

If you open up more than one window, wind buffeting may stop. Wind buffeting is most likely if you open only one window at the back of your car. 

Opening front windows or opening both back windows is less likely to lead to wind buffeting. Opening windows to stop wind buffeting from a sunroof might not work, but it’s worth trying if you don’t have a wind deflector. 

What is a Wind Deflector?

Wind deflectors work wonders to reduce drag from sunroofs. If you have a newer car with a wind deflector, you can usually open the sunroof without creating drag. 

Usually, you have to drive over the speed limit for there to be a significant amount of drag with a wind deflector. They really do work, so there won’t be much drag at slower speeds. Some sunroof wind deflectors are better than others. 

Weight Also Matters

The weight of a sunroof can also slow a car down. If your sunroof weighs 100 pounds and your car weighs only 3000 pounds, that increases your total weight by a few percent. This is enough to noticeably lower performance and fuel mileage. 

If you want a sunroof, get it – it’s worth the somewhat lower performance and the price. However, don’t get a sunroof that you don’t really want and will hardly use. That is a waste of money and will slow your car down. 

Does a Sunroof Also Create Drag When it’s Closed?

A closed sunroof almost certainly won’t create much drag. It is mostly flat and won’t affect the airflow enough to slow a car down. However, the weight of a closed sunroof makes a difference. 

Adding anything that weighs your car down and/or creates drag can slow your car down. Doing something as small as adding a roof rack may make your vehicle use 5% more fuel. These additions are still worth it if you really want them, but they have drawbacks. 

Why Do People Have Sunroofs?

Sunroofs are stylish, plus they give you fresh air and more sunlight. They can make a long summer drive much better. Newer sunroofs are much better and often cover nearly the whole roof. 

Sunroofs are good even in colder weather. You don’t have to open a sunroof to let lots of light into your car. Driving on a bright but snowy day is great with the sunroof closed. 

Are Sunroofs Expensive? 

Not really. They do add $500 or $2000 to a car’s price, but they are less expensive than some people would expect. If you sell your car, a sunroof improves the price you can get for it. 

Are Sunroofs Heavy?

Sunroofs often weigh 75 or 100 pounds. Impressive panoramic sunroofs weigh 120 to 200 pounds. This can increase a small vehicle’s weight significantly. 

Key Takeaways

• Yes, opening a sunroof will create drag. It may even create wind buffeting, which is noisy and can make your car harder to control. 
• These problems are smaller at slower speeds and are smaller if you have a wind deflector. A lot of the time, it’s worth it to drive with the sunroof open. 
• Sunroofs are worth it. It’s great to drive with the sunroof open on a hot day or with the sunroof closed on a cold but sunny day. They do weigh your car down a little, but they’re worth having.