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Quick answer: yes. A roof rack adds drag, and the cost rises with speed. Per the U.S. Department of Energy, a large, blunt roof-top cargo box can cut fuel economy by about 2% to 8% in the city, 6% to 17% on the highway, and 10% to 25% at 65 to 75 mph. A rear-mount (hitch) cargo box or tray costs only about 1% to 2% in the city and 1% to 5% on the highway. The DOE gives no figure for bare crossbars; they add some drag too, so taking them off when you don’t need them is a sensible habit.
Last updated: October 2026.
How we wrote this: the fuel numbers come from fueleconomy.gov (U.S. Department of Energy), which cites Oak Ridge National Laboratory tests. We did not run our own MPG tests. Product details come from the listings, and we say so where it matters.
How Much Does a Roof Rack Affect Gas Mileage?
Short answer: it depends most on what’s on top and how fast you drive. Here are the published DOE figures (bare crossbars are not quantified):
| Setup | City | Highway | 65–75 mph |
|---|---|---|---|
| Large, blunt roof-top cargo box | 2%–8% lower | 6%–17% lower | 10%–25% lower |
| Rear-mount (hitch) cargo box or tray | 1%–2% lower | 1%–5% lower | Not listed |
Source: fueleconomy.gov (U.S. Department of Energy). The tests used a small sedan, a standard-size SUV, one roof-top box (20 x 40 x 50 inches) and one rear cargo tray. Boxes of other sizes and shapes may give different results, and the DOE doesn’t give a separate figure for empty crossbars.
Check your own car’s MPG
Fill the tank, reset the trip meter, and drive your usual route for about 100 miles without the rack. Refill and divide miles by gallons. Then repeat with the rack (and again with it loaded). Use the same route and similar speeds, or the weather and traffic will hide the difference.
Why a Roof Rack Lowers Fuel Economy
Short answer: aerodynamic drag. Your car is shaped to let air flow smoothly over the roof. Bars, boxes and gear break up that flow and create turbulence, so the engine works harder to hold the same speed.
Aerodynamic drag grows with the square of speed: in still air, going from 55 to 75 mph raises the drag force by about 86% (that is drag, not an 86% MPG loss). That is why the highway numbers above are higher than the city ones. At highway speeds drag tends to dominate; weight also matters, especially when accelerating (the DOE puts an extra 100 lb at about 1% MPG).
What makes the loss bigger
- What’s on top: you can expect bare bars to cost less than a box, bikes or a kayak. Upright bikes and boards act like a sail.
- Shape and size: the DOE tested a large, blunt box and notes that other sizes and shapes may give different results.
- Bar profile: makers of wing and teardrop bars say they disturb the air less than square or round bars.
- Speed and wind: highway speed and headwinds make everything worse.
How to Cut the Fuel Penalty: 6 Steps
Short answer: take the rack off when you don’t need it, move cargo to the hitch when you can, and slow down a little on the highway.
1. Remove the rack and box when not in use
The DOE says removing an external cargo container when it’s not in use saves fuel. Bare bars add some drag too, every day they stay on. Our guide to removing roof racks shows how.
2. Use aero (wing-shaped) crossbars
If you leave bars on all season, consider a wing or teardrop profile like the Thule WingBar Evo or Yakima JetStream. Both makers say their shapes cut drag and noise.
3. Add a wind fairing
A fairing is a curved shield on the front bar that pushes air up and over the rack. Makers claim it cuts wind noise and drag; we found no independent figure for its effect on MPG. If your rack hums or whistles, see why roof racks whistle.
4. Pack smart
Pick a box no bigger than you need, mount it in the orientation its maker specifies, and strap loads tight so nothing flaps. Keep heavy items inside the car.
5. Move cargo to the hitch
Per the DOE, a rear-mount box or tray costs far less fuel than a roof box. It needs a hitch and blocks the hatch on some cars.
6. Slow down 5 to 10 mph
With cargo on the roof, speed matters a lot: in the table above, the DOE’s 65–75 mph figures are the highest. The DOE also lists slowing down 5 to 10 mph as a general fuel saver. Avoid rapid acceleration and hard braking too; the DOE counts aggressive driving as a fuel waster.
Quick Picks: Fairings, Aero Bars and Lower-Drag Cargo
| Product | Best for | Price tier | Key strength |
|---|---|---|---|
| Thule AirScreen XT fairing | Thule WingBar Evo / Edge, AeroBlade, SquareBar Evo | Premium | Tool-free clip-on, keeps T-track access |
| Yakima WindShield fairing | Yakima StreamLine or round bars | Premium | Pushes air up and over the rack |
| Rhino-Rack RF4 fairing, 50 in | Rhino-Rack crossbars | Mid-range | 50-inch deflector, low-profile look |
| DREAMOTOR universal fairing, 42 in | Factory crossbars on a budget | Budget | PP plastic, fits many factory bars |
| Thule WingBar Evo, 50 in | Replacing square or round bars | Premium | Wing profile with wind diffuser |
| Yakima JetStream bars, 60 in | Yakima tower owners | Premium | Teardrop aluminum, wind-tunnel shaped |
| INNO Wedge 660 low-profile box | A slimmer roof box | Premium | Low-profile, dual-side opening |
| CURT 18153 hitch basket | Moving cargo off the roof | Mid-range | 500 lb rating, folds up when empty |
Price tiers are relative; the card on each pick shows the live Amazon price.
8 Picks to Cut Roof-Rack Drag and Noise
1. Best Fairing for Thule Aero Bars: Thule AirScreen XT Wind Fairing
- Attaches to Thule WingBar Evo, WingBar Edge, AeroBlade, AeroBlade Edge and SquareBar Evo with included hardware
- Around the bar tool-free mounting allows for quick T-track access
- Clip-on design requires no tools for assembly or installation
Bottom line: if you already run Thule bars, this is the fairing made for them. Per the listing it attaches to the WingBar Evo, WingBar Edge, AeroBlade, AeroBlade Edge and SquareBar Evo with the included hardware, and the clip-on design needs no tools.
The around-the-bar mount leaves the T-track open, so you can still add a bike or ski mount. The listing gives no MPG figure for it.
Who it’s NOT for: Yakima, Rhino-Rack or factory bars. Check that your exact Thule bar is on the fit list.
2. Best Fairing for Yakima Bars: YAKIMA WindShield Fairing
- Compatible: Universal mounting attachment works with any YAKIMA bar – StreamLine or round; Fits square bars and most fac…
- Aerodynamic: Moves airflow up and over the rack to reduce drag and quiet wind noise
- Easy installation: Installs in 25 minutes; Secure to any crossbar quickly and easily with included tools
Bottom line: Yakima’s own fairing. The listing says its universal mount works with any Yakima bar, StreamLine or round, and also fits square bars and many factory bars.
Yakima says it moves air up and over the rack to cut drag and wind noise, and that install takes about 25 minutes with the included tools. Choose the fairing width with Yakima’s sizing guidance and your crossbar width.
Who it’s NOT for: drivers who rarely carry anything up top; they may do better taking the bars off between trips.
3. Best for Rhino-Rack Owners: Rhino-Rack Wind Fairing 50 Inch (RF4)
- QUIET & AERODYNAMIC – The Rhino-Rack Wind Fairing has been engineered to minimize wind noise while driving. Hearing the …
- WIND DEFLECTOR – The Rhino-Rack roof rack fairing deflects air around your load and cross bars, which keeps things quiet…
- STYLISH – We’ve styled this wind fairing so that it enhances the sleek design of your vehicle and roof racks.
Bottom line: a 50-inch fairing from Rhino-Rack. The listing says it deflects air around your load and crossbars to keep things quiet.
Fit depends on your bar profile, so confirm on the listing that it works with your bars (Rhino-Rack or other) and that your bars are wide enough for a 50-inch fairing.
Who it’s NOT for: narrow cars whose bars are too short for a 50-inch fairing.
4. Best Budget Universal Fairing: DREAMOTOR 42-Inch Roof Rack Wind Fairing
- 【Reduce wind noise】Upgrade your roof rack system with this universal roof rack fairing, designed to minimize wind noise …
- 【Premium Material】Constructed from high-quality PP, this roof rack fairing offers excellent impact resistance, UV protec…
- 【Wide Application】The roof rack fairing roof rack wind deflector is specifically designed for crossbars with a bar width…
Bottom line: the low-cost way to try a fairing on factory crossbars. Per the listing it is 42 inches (106 cm) wide, made of PP plastic, and sold to fit many factory bars on cars like the Civic and Camry.
Its main promise is less wind noise. The listing gives a range of bar widths it fits, so measure your bars first.
Who it’s NOT for: owners of Thule or Yakima aero bars, who will get a cleaner fit from the brand’s own fairing.
5. Best Aero Crossbars (Thule): Thule WingBar Evo 50-Inch Aluminum
- Includes easy-to-install load carrier feet and Thule wing bar evo load bars
- Upper T-track with quick access interface allows smooth installation and removal of accessories
- Wind diffuser technology disturbs airflow to reduce Noise and drag for improved fuel economy
Bottom line: if your bars are old square or round steel, a wing-shaped bar is worth a look. Thule says the WingBar Evo’s wind diffuser reduces noise and drag for better fuel economy.
The upper T-track accepts compatible T-track accessories. This listing says load carrier feet are included; check which feet they are, and use Thule’s fit guide to confirm they fit your car and whether you also need a fit kit.
Who it’s NOT for: cars with factory crossbars you are happy with; a fairing is a smaller change.
6. Best Aero Crossbars (Yakima): YAKIMA JetStream Bar, Set of 2, 60 Inch
- JetFlow Teardrop Shape: Aerodynamic crossbar designed with wind tunnel tested for peak performance that minimizes drag, …
- Aluminum Construction: Crafted from seamless extruded aluminum, these crossbars offer a perfect blend of strength and li…
- JetTruss Internal Support: Engineered for strength without weight, the JetTruss internal support system provides unparal…
Bottom line: Yakima’s aero bar. The listing describes a teardrop (JetFlow) shape designed in a wind tunnel to cut drag, made from extruded aluminum with an internal truss for strength.
These are bars only. They need compatible Yakima towers plus any clips or fit kit specified for your car, so use Yakima’s fit guide first.
Who it’s NOT for: anyone who doesn’t want to buy towers too. These bars alone won’t mount to a car.
7. Best Low-Profile Roof Box: INNO Wedge 660, 11 cu ft
- DUAL-SIDE OPENING FOR EASY LOADING – Convenient dual-side opening design allows loading and unloading cargo from either …
- 11 CU. FT. ROOFTOP STORAGE CAPACITY – Provides 11 cubic feet of rooftop cargo storage and accommodates up to 4 snowboard…
- MEMORY MOUNT SYSTEM FOR FAST INSTALLATION – Memory Mount system allows quick installation and removal after the initial …
Bottom line: if you need a roof box, this is a slim option. The Wedge 660 is sold as a low-profile, 11 cu ft box that opens from both sides and fits aero and square bars, per the listing.
Any roof box costs fuel. The DOE figures above were measured with one large, blunt box; the Wedge 660’s effect on MPG isn’t established by that test or any we found. Take it off between trips.
Who it’s NOT for: people who need to carry a lot of bulky gear. 11 cu ft is mid-size; see our roof box guide for bigger boxes.
8. Best Fuel-Saving Alternative: CURT 18153 Folding Hitch Cargo Basket, 60 x 24 in
- 6″ tall sides keep items more secure during travel
- Frees up space inside the vehicle for passengers and cargo
- Constructed from heavy-duty, tubular steel
Bottom line: the DOE says rear-mount cargo trays cost much less fuel than a roof box (1% to 5% on the highway vs 6% to 17%). This CURT basket is 60 x 24 inches with 6-inch sides, made of tubular steel and listed at 500 lb.
Keep basket plus cargo within your vehicle’s and hitch’s tongue-weight limits and the basket’s 500 lb rating, whichever is lower. Check the receiver size on the listing and the ratings in your owner’s manual. See our hitch cargo carrier guide for more options.
Who it’s NOT for: cars without a trailer hitch, or hitches with a low tongue-weight limit.
Handling and Noise
Weight on the roof raises the center of gravity, so the car can lean more in corners. Tall cargo also gives crosswinds more to push on. Stay within both your car’s roof-load limit (in the owner’s manual) and the rack’s rating, counting the weight of the rack and box too. Check that the bars are tight before a long trip and at stops along the way.
The same turbulence that costs fuel also makes noise. For fixes, see how to make a roof rack quieter and roof box noise.
Black Friday Tip and Gift Idea
A wind fairing is a practical gift for a driver whose bars stay on all year, but it must match their bar brand and width. Check those first.
Black Friday tip: decide on the exact model and size now, then compare the live price on the card during Black Friday week. Our note on when roof racks go on sale has more timing tips.
Frequently Asked Questions
Will removing my roof rack make a noticeable difference in MPG?
It varies by car and setup. The DOE says removing an external cargo container when not in use saves fuel, and bare bars add some drag too. Test it on your own car with a before-and-after fill-up.
How much does a roof box reduce gas mileage?
Per the DOE, a large, blunt roof-top box can lower fuel economy by about 2%–8% in the city, 6%–17% on the highway and 10%–25% at 65–75 mph.
Do empty roof racks affect gas mileage?
They add some drag, so some loss is likely, mostly at highway speed. The DOE doesn’t publish a figure for bare crossbars, and makers of wing-shaped bars say their shapes cut drag.
Do wind fairings improve gas mileage?
Makers say fairings reduce wind noise and drag, but we found no independent MPG figure, so treat any fuel saving as unproven. The noise benefit is the main reason to buy one.
Is a hitch cargo carrier better for fuel economy than a roof box?
Yes. Per the DOE, rear-mount boxes or trays lower fuel economy by only 1%–2% in the city and 1%–5% on the highway, much less than a roof box.
Do roof bars affect fuel economy at low speed?
Less. Aerodynamic drag rises with the square of speed, so the DOE’s city figures are lower than its highway figures.
Does a roof rack increase fuel consumption?
Yes. Fuel consumption (litres per 100 km) is the other side of MPG: when fuel economy drops, consumption rises by a bit more. For example, a 10% drop in MPG means about 11% more fuel per 100 km, and a 20% drop means 25% more. The DOE figures above are given as fuel-economy losses.
Does an empty roof box still use more fuel?
Yes. The drag comes mostly from the box’s shape and size, which don’t change when it’s empty. The DOE says removing an external cargo container when you’re not using it saves fuel, so take an empty box off between trips.
Do roof platforms and baskets affect gas mileage?
Expect some loss. The DOE doesn’t publish a figure for flat platforms or baskets, but like bars they add drag, and gear strapped on top adds more. Keep loads low and tight, and remove the platform or basket if it isn’t needed for a while.
The Bottom Line
A roof rack does lower fuel economy. The DOE reports a 10%–25% drop for a large, blunt roof-top box at 65–75 mph. Take the rack off when you don’t need it, consider aero bars if it stays on, carry cargo on the hitch when you can, and ease off the speed. Buy a fairing for noise; its fuel saving is unproven. If you are still choosing a rack, start with which roof rack to buy.
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