# Vehicle air vents and drag? **URL:** \ **Category:** Power/Fuel\ **Created:** [July 24, 2023, 7:01pm UTC](https://community.cartalk.com/t/vehicle-air-vents-and-drag/191888 "2023-07-24T19:01:23Z")\ **Posts on this page:** 17\ **Page:** 1
**Author:** ![levi99522\_181953](https://avatars.discourse-cdn.com/v4/letter/l/f0a364/32.png) [@levi99522\_181953](https://community.cartalk.com/u/levi99522_181953)\ **Post date:** [July 24, 2023, 7:01pm UTC](https://community.cartalk.com/t/vehicle-air-vents-and-drag/191888/1 "2023-07-24T19:01:23Z")
This might be a stupid question, but I was wondering if I close the air vents in my car or I turn on the recirculation so outside air can’t enter the cabin will it decreasd drag just like rolling up the windows? 😅 ---
**Author:** ![VDCdriver](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/vdcdriver/32/30_2.png) [@VDCdriver](https://community.cartalk.com/u/VDCdriver)\ **Post date:** [July 24, 2023, 7:05pm UTC](https://community.cartalk.com/t/vehicle-air-vents-and-drag/191888/2 "2023-07-24T19:05:40Z")
It’s not a stupid question, but IF it resulted in decreased drag, the reduction would so slight as to be impossible to quantify. But, here is another question: If it did result in slightly decreased drag, would the theoretical _miniscule_ increase in gas mileage be worth it, considering the probability of developing heat stroke or–even worse–being poisoned by CO fumes? ---
**Author:** ![levi99522\_181953](https://avatars.discourse-cdn.com/v4/letter/l/f0a364/32.png) [@levi99522\_181953](https://community.cartalk.com/u/levi99522_181953)\ **Post date:** [July 24, 2023, 7:10pm UTC](https://community.cartalk.com/t/vehicle-air-vents-and-drag/191888/3 "2023-07-24T19:10:07Z")
Of course it is not worth it, but I was just curious of how much it would decrease drag. I somehow imagined it to close off some vent at the front of the car therefor helping with mileage or acceleration 🧐 ---
**Author:** ![bing](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/bing/32/4619_2.png) [@bing](https://community.cartalk.com/u/bing)\ **Post date:** [July 24, 2023, 7:11pm UTC](https://community.cartalk.com/t/vehicle-air-vents-and-drag/191888/4 "2023-07-24T19:11:01Z")
Just drive along at a constant speed, watch the computer mpg calculator and switch back and forth from vent to no vent. Report back. ---
**Author:** ![levi99522\_181953](https://avatars.discourse-cdn.com/v4/letter/l/f0a364/32.png) [@levi99522\_181953](https://community.cartalk.com/u/levi99522_181953)\ **Post date:** [July 24, 2023, 7:14pm UTC](https://community.cartalk.com/t/vehicle-air-vents-and-drag/191888/5 "2023-07-24T19:14:15Z")
I tried doing it but my car has no cruise control and the measurements are so incorrect, all over the place. That is why I’m asking because even if the gains are very miniscule I just want to know. ---
**Author:** ![weekend-warrior](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/weekend-warrior/32/26122_2.png) [@weekend-warrior](https://community.cartalk.com/u/weekend-warrior)\ **Post date:** [July 24, 2023, 7:17pm UTC](https://community.cartalk.com/t/vehicle-air-vents-and-drag/191888/6 "2023-07-24T19:17:52Z")
There was a show on something similar on Myth Busters. Only with the windows open and a/c off vs a/c on and windows closed. If I remember correctly, it did not make much of a difference. If you want to decrease drag you are better off making sure your tires are inflated correctly or a lb. or 2 over. ---
**Author:** ![VDCdriver](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/vdcdriver/32/30_2.png) [@VDCdriver](https://community.cartalk.com/u/VDCdriver)\ **Post date:** [July 24, 2023, 7:22pm UTC](https://community.cartalk.com/t/vehicle-air-vents-and-drag/191888/7 "2023-07-24T19:22:36Z")
> [@weekend-warrior](#): > > If you want to decrease drag you are better off making sure your tires are inflated correctly or a lb. or 2 over. +1 That, plus buying tires with a low rolling resistance, getting rid of the junk in the trunk, maintaining the engine properly, accelerating gently, not warming-up the engine, and NOT tailgating. If the OP doesn’t know why tailgaters inevitably use more gas, he should ask us. ---
**Author:** ![bing](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/bing/32/4619_2.png) [@bing](https://community.cartalk.com/u/bing)\ **Post date:** [July 24, 2023, 8:11pm UTC](https://community.cartalk.com/t/vehicle-air-vents-and-drag/191888/8 "2023-07-24T20:11:40Z")
Maybe a good wax and polish would make a difference. It usually makes the car run better. It is one of those mysteries never to be known. ---
**Author:** ![VDCdriver](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/vdcdriver/32/30_2.png) [@VDCdriver](https://community.cartalk.com/u/VDCdriver)\ **Post date:** [July 24, 2023, 8:16pm UTC](https://community.cartalk.com/t/vehicle-air-vents-and-drag/191888/9 "2023-07-24T20:16:00Z")
> [@bing](#): > > Maybe a good wax and polish would make a difference. It usually makes the car run better. When I was a kid, one of the car washes in town had a large sign stating that, “A clean car runs better”. 🤥 ---
**Author:** ![Mustangman](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/mustangman/32/44130_2.png) [@Mustangman](https://community.cartalk.com/u/Mustangman)\ **Post date:** [July 24, 2023, 8:29pm UTC](https://community.cartalk.com/t/vehicle-air-vents-and-drag/191888/10 "2023-07-24T20:29:15Z")
The effect of vents open or recirc is likely un-measurable… There is likely a benefit to this but tiny. Now adding golf-ball like dimples (3 inch diameter) all over your car WILL get you better mileage. Mythbusters did that to a Ford Taurus and found a significant improvement. It was a huge headache to construct and looked ridiculous but it did _work_… ---
**Author:** ![Renegade](https://avatars.discourse-cdn.com/v4/letter/r/b4bc9f/32.png) [@Renegade](https://community.cartalk.com/u/Renegade)\ **Post date:** [July 24, 2023, 8:49pm UTC](https://community.cartalk.com/t/vehicle-air-vents-and-drag/191888/11 "2023-07-24T20:49:21Z")
> [@Mustangman](#): > > Now adding golf-ball like dimples (3 inch diameter) all over your car WILL get you better mileage. How would that work I would think that would cause decreased air flow. ---
**Author:** ![VDCdriver](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/vdcdriver/32/30_2.png) [@VDCdriver](https://community.cartalk.com/u/VDCdriver)\ **Post date:** [July 24, 2023, 8:52pm UTC](https://community.cartalk.com/t/vehicle-air-vents-and-drag/191888/12 "2023-07-24T20:52:03Z")
> [@Renegade](#): > > How would that work I would think that would cause decreased air flow. I don’t recall their explanation, but the Myth Busters guys seemed to prove the thesis that golf ball-like dimples on the car decreased drag. ---
**Author:** ![Mustangman](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/mustangman/32/44130_2.png) [@Mustangman](https://community.cartalk.com/u/Mustangman)\ **Post date:** [July 24, 2023, 9:17pm UTC](https://community.cartalk.com/t/vehicle-air-vents-and-drag/191888/13 "2023-07-24T21:17:46Z")
> [@Renegade](#): > > How would that work The idea is to create a small amount of turbulence to decrease drag. The turbulence reduces the detachment of air at the back of the car causing a smaller wake so less drag. Same effect as a “Gurney flap” on a race car wing except round! Works the same on a golf ball. The car went from 26 mpg to over 29 mpg in their test. They covered the car in clay to form the dimples and loaded the clay into the car for the “base” test. ---
**Author:** ![jtsanders](https://avatars.discourse-cdn.com/v4/letter/j/c2a13f/32.png) [@jtsanders](https://community.cartalk.com/u/jtsanders)\ **Post date:** [July 24, 2023, 9:23pm UTC](https://community.cartalk.com/t/vehicle-air-vents-and-drag/191888/14 "2023-07-24T21:23:05Z")
One way to look at it is that when the vent is closed incoming air is met by a solid wall that will impede forward motion. OTOH if the vent is open the air will hit a solid wall eventually whether the air hits the seats or the rear window. Either way the air makes a hard stop somewhere. Given the size of the vent inlet compared to the other forward facing surfaces on the car, the effect is immeasurable small. ---
**Author:** ![LoudThunder](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/loudthunder/32/27769_2.png) [@LoudThunder](https://community.cartalk.com/u/LoudThunder)\ **Post date:** [July 24, 2023, 9:33pm UTC](https://community.cartalk.com/t/vehicle-air-vents-and-drag/191888/15 "2023-07-24T21:33:33Z")
> [@weekend-warrior](#): > > Myth Busters. That reminds me of another Myth Busters test… How fast do you have to drive in the rain in a convertible with top down to keep from getting wet… > **[MythBusters Episode 124: Car vs. Rain](https://mythresults.com/car-vs-rain)** > > The MythBusters test whether you can stay dry in the rain in a convertible by driving really fast and whether explosives and lasers can pop popcorn. The Myth Busters did their test in 2009, but in the mid 1970’s some friends were driving on the New York State Thruway. When they started out, it was not raining, but part way through, it started to rain, but since they were going pretty fast and they were not getting wet, they left the top down and drove on in the rain… That is until it was time to exit. While exiting, they tried to put the roof up, but they were still going too fast for the roof to raise up and the wind bent the mechanism and the front part of the roof that attached to the windshield no longer met up. They ultimately had to tie the roof down with a rope. After it was “repaired” it never worked right again… And that’s no Myth… L 😄 L… ---
**Author:** ![LoudThunder](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/loudthunder/32/27769_2.png) [@LoudThunder](https://community.cartalk.com/u/LoudThunder)\ **Post date:** [July 24, 2023, 9:38pm UTC](https://community.cartalk.com/t/vehicle-air-vents-and-drag/191888/16 "2023-07-24T21:38:21Z")
> [@Mustangman](#): > > your car WILL get you better mileage. I do not know about better milage, but the dimples on a golf ball has it’s own trade secrets as the dimples allow the golf ball to fly farther… Some thing I imagine that Thelma and Louise should have looked into… L 😄 L … ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [July 24, 2023, 10:07pm UTC](https://community.cartalk.com/t/vehicle-air-vents-and-drag/191888/17 "2023-07-24T22:07:46Z")
> [@LoudThunder](#): > > imples on a golf ball has it’s own trade secrets as the dimples allow the golf ball to fly farther Golf balls at first were designed to be smooth spheres. Experienced golfers soon learned these smooth balls would go further and straighter after they has been used a few rounds and their surfaces battered and roughened up. Golf ball companies determined the roughened surface improved the airflow behavior. Then they had to figure out a way to make new golf balls with a rough surface. Dimples.