How Much MPG Do You Really Lose With a Bed Rack?
š What's in this guide
The Short Answer
Yes, a bed rack affects gas mileage. No, it's probably not as bad as you think. Most bed rack setups cost somewhere between 1% and 8% of your fuel economy, depending on how high your gear sits and how much of it there is. That's a smaller hit than a roof-mounted cargo box, which can run 10-25% at highway speeds. The difference comes down to one thing: a bed rack keeps your load lower and closer to the truck's natural shape, while a roof box sits in the fastest-moving air above the cab.
The honest version: nobody can give you an exact number without a dyno and a controlled test track, because your specific hit depends on rack height, total weight, what's strapped to it, and how fast you drive. What we can do is show you the real published data on cargo aerodynamics, plus what actual truck owners are reporting, so you can estimate your own setup instead of guessing.
How a Bed Rack Actually Costs You Mileage
There are exactly two mechanisms at play, and almost everything else is noise.
Aerodynamic drag
Air doesn't care that your truck bed is "supposed" to be empty. Once something breaks the airflow above the bed rails, the truck has to push more air out of the way, and the engine burns more fuel to maintain speed. Drag increases roughly with the square of your speed, which is why this barely matters at 30 mph in town and matters a lot at 75 mph on the interstate.
Added weight
A steel bed rack, a rooftop tent, recovery gear, water jugs ā it all adds rolling mass. Heavier vehicles need more energy to accelerate and to climb grades. This effect is smaller than drag at highway speed but it's constant, in town and on the highway alike.
A bare bed rack with nothing mounted to it barely registers on either front ā it sits low, inside the truck's existing profile, and weighs a fraction of what a loaded rack does. The real cost shows up once you start stacking gear on top of it, especially gear that's tall, boxy, or sits above the cab line.
The Real Numbers (With Sources)
Most articles on this topic stop at "it depends." Here's what's actually been measured.
2-8%Roof cargo box, city driving
6-17%Roof cargo box, highway
10-25%Roof cargo box, 65-75 mph
That's the U.S. Department of Energy's published figure for a large, blunt roof-top cargo box ā the worst-case scenario for rooftop drag.
Source: U.S. Department of Energy, "Driving More Efficiently" ā figures are for general cargo boxes and rear cargo trays, the closest tested analog to a truck bed rack; no government study has tested bed racks directly.
Now here's the number that actually matters for a bed rack: a rear or bed-mounted cargo box or tray ā much closer in mounting position to a truck bed rack than a roof box is ā only costs about 1-2% in city driving and 1-5% on the highway, according to the same DOE data set. A bed rack isn't identical to a rear cargo tray, but it's a far closer cousin to it than to a roof box, which is exactly why bed racks generally hit your mileage less than people assume.
Weight rule of thumb: the EPA estimates that every extra 100 lbs of cargo costs a vehicle roughly 1% in fuel economy. A loaded bed rack with a rooftop tent and recovery gear can easily add 150-300+ lbs, so that's a separate, stackable hit on top of the drag number above.
Source: fueleconomy.gov, U.S. EPA driving habits data.
Source: fueleconomy.gov, U.S. EPA driving habits data.
Add the two together and you get a reasonable estimate: drag from height plus a percentage point or two from weight. A bed rack sitting below the cab with a moderate load is doing roughly what a rear cargo tray does. A bed rack stacked to roof height with a tent and full camp kit starts creeping toward roof-box territory.
Bed Rack vs. Roof Rack: Why Position Matters More Than Presence
This is the part competitors gloss over: a bed rack and a roof rack are not the same aerodynamic problem just because they're both "racks." Position in the airflow is the deciding factor.
| Mounting position | Typical drag profile | Why |
|---|---|---|
| Roof rack / roof box | Highest | Sits in the fastest, most undisturbed airflow above the cab |
| Bed rack, above cab height | Moderate-high | Breaks airflow similarly to a roof box once gear clears the cab line |
| Bed rack, at cab height | Moderate | Gear rides in the truck's existing wake, less new frontal area |
| Bed rack, below cab height | Low | Stays inside the vehicle's natural air shadow, closest to a rear cargo tray |
This is also why a low profile rack and a full height rack aren't just a style choice ā height is the single biggest lever you control on this whole question. If mileage is a real priority for you, that decision matters more than which brand of bed rack you buy.
What Real Truck Owners Report
Published lab data is one half of the picture. Owner-reported numbers from truck forums are the other ā and they line up with the DOE data closely enough to trust the pattern, even though every one of these is a self-reported, uncontrolled estimate.
| Setup | Reported MPG | Notes |
|---|---|---|
| Cab-height bed rack + RTT, mixed driving | ~1 mpg gain vs. open bed | Tent height matched cab line, minimal added drag |
| Bed rack + RTT + winch bumper + lift + 33s | ~16 mpg | Multiple modifications stacked, hard to isolate the rack's share |
| Bed rack + RTT, low-profile, 70 mph highway | ~20 mpg | Tent stayed below roofline |
| Roof-top tent + ~600 lbs gear (no bed rack) | ~4 mpg loss | Tall tent fully exposed to highway airflow |
| Cab-height rack, empty | No noticeable change | "Won't hurt mileage any more than your mirrors," per owner |
Sources: TacomaWorld owner thread, Expedition Portal owner thread.
The pattern is consistent: owners who kept gear at or below cab height saw little to no change. Owners who stacked tall gear above the roofline, especially at sustained highway speed, reported the biggest losses. Total vehicle weight and tire/lift modifications muddy individual numbers, but the height effect shows up in every thread.
š§ MPG Impact Estimator
Answer two quick questions for a rough estimate based on the DOE ranges above. This is a directional estimate, not a guarantee ā your actual mileage depends on your truck, tires, and driving style.
How to Minimize the Hit
- Keep the load at or below cab height. This is the single biggest factor in every data source above ā bigger than rack brand, material, or even total weight.
- Go lighter where it counts. A lighter rack material shaves a little weight, though height matters more than the few pounds saved between steel and aluminum ā pick material for durability first, and treat the mileage difference as a bonus, not the deciding factor.
- Don't carry what you don't need. Full water jugs and a stocked fridge add up fast under the EPA's 100-lb rule. Pack for the trip you're taking, not every trip you might take.
- Strap gear tight and tucked in. Loose straps and gear that catches wind add drag beyond what its size alone would suggest.
- Pair with a tonneau cover when the rack allows it. Some tonneau covers can smooth airflow under a bed rack setup ā check your rack and cover compatibility first, since not every mounting style works together.
- Remove the rack for trips where you don't need it. If you only go off-grid a few times a year, a quick-release rack saves you the daily-driver penalty.
Quick Comparison Table
| Setup | Typical mileage impact | Rating |
|---|---|---|
| Empty bed rack, below cab height | ~0-1% | Minimal |
| Loaded bed rack, at/below cab height | ~1-5% | Low |
| Loaded bed rack, above cab height (tent/cargo) | ~5-12% | Moderate |
| Roof rack, loaded box, highway speed | ~6-17% | Moderate-High |
| Roof rack, loaded box, interstate speed | ~10-25% | High |
FAQ
Barely. An empty rack mounted within the truck's existing profile adds minimal frontal area and only a small amount of weight. Most owners report no noticeable change until they start loading gear onto it.
Generally yes, because it keeps gear lower in the airflow. A bed rack loaded above the cab line starts to behave more like a roof box, so the height of your specific load matters more than which part of the truck it's mounted to.
It can, by smoothing airflow over an otherwise open bed, but only if your rack and cover are actually compatible with each other. Check mounting type before assuming the two will work together.
The weight difference between a steel and aluminum rack is usually small enough that it's a minor factor next to height and total load. Choose material based on durability and budget, not a meaningful mileage gain.
Real owner reports range from roughly 1 mpg gained (low-profile tent, cab height) to about 4 mpg lost (tall tent, sustained highway speed, heavy gear load). Your number depends mostly on tent height and how fast you drive.
No. Drag-related losses are much smaller at city speeds and grow sharply at highway and interstate speeds, since aerodynamic drag increases with the square of speed. Weight-related losses stay roughly constant regardless of speed.
Not precisely. Real-world mileage varies with tires, wind, terrain, and driving style. The DOE ranges and the estimator above give a reasonable directional answer, not a lab-grade measurement.
Verdict
A bed rack will cost you some mileage, but the published data and the owner reports agree on the same conclusion: it's usually a modest hit, not a dramatic one, as long as your load stays near or below cab height. The real number to watch isn't the rack itself ā it's how tall and how heavy your loaded setup ends up being once the tent, fridge, and recovery gear are strapped on.
- Keep gear at or below cab height whenever the build allows it
- Budget roughly 1-5% mileage loss for a sensible, low-profile loaded setup
- Expect more like 5-12%+ once gear clears the roofline, especially at highway speed
- Treat rack material and brand as secondary to height and total load
Still deciding which rack to buy before you worry about MPG? Our complete bed rack buying guide covers material, height, mounting, and load capacity together.
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