Do Tonneau Covers Improve Gas Mileage? What the Tests Actually Show

“Pays for itself in gas” is one of the most repeated tonneau cover claims, and some makers put a number on it: TruXedo’s Lo Pro marketing (via etrailer) says “up to 10 percent,” and Tyger’s T5 page claims “10–13%.” We went looking for the evidence behind numbers like that. There’s some, it points in the right direction, and it’s much smaller and less certain than the marketing.

We haven’t run fuel tests ourselves. Everything below comes from published sources we read on November 12, 2026, and each is linked. Where a result comes from a test, we name who ran it.

The short answer

A cover probably improves highway fuel economy slightly on many trucks. Nobody has published a solid, controlled figure for an aftermarket cover on a gas pickup. Car and Driver, after testing six covers, put it plainly: “we’ve yet to see any solid empirical data on the subject.” Don’t buy a cover to save fuel; buy it for security and weather, and treat any saving as a bonus.

What the evidence says

Wind-tunnel work: drag drops a little

The strongest controlled result is old and measures drag, not fuel. Texas Tech researchers (SAE paper 881874, 1988) tested pickup drag-reduction devices in a low-speed wind tunnel and at full scale in the Lockheed wind tunnel. A cover over the rear portion of the bed cut aerodynamic drag 5–6% and lift 30%; a cover combined with a wing reduced drag about 17% on a scale model.

Drag and fuel aren’t the same thing. At highway speed, only part of a gas truck’s fuel goes to pushing air out of the way; the rest goes to rolling resistance, drivetrain losses and the engine’s own inefficiency. So a 5–6% drag cut means a smaller percentage fuel saving, and less still at lower speeds. Truck shapes have also changed a lot since the 1980s.

The EPA hint: Ram 1500 HFE

Car and Driver points to the 2015 Ram 1500 HFE EcoDiesel, an efficiency-focused trim that was rated 29 mpg highway by the EPA with a factory-installed tonneau, against 28 mpg for the standard EcoDiesel. That’s about a 3% better rating. But the HFE had other efficiency changes too, so the cover’s share of that 1 mpg isn’t isolated.

The big number: an electric truck at 75 mph

Car and Driver’s range testing of the Tesla Cybertruck produced the most dramatic result: at a steady 75 mph on a 6.6-mile oval, the truck used 58.3 kWh per 100 miles with its factory roll-top closed and 64.2 with it open, about 10% more range closed. Lowering the tailgate as well barely mattered (64.0).

It’s a real measurement, but not a forecast for your F-150. It’s one electric truck with an integrated cover designed with the body, at a sustained high speed. Electric trucks lose a larger share of their energy to drag than gas trucks do, because their drivetrains waste less elsewhere. Treat it as an upper bound.

Tailgate down doesn’t help

The old trick of driving with the tailgate down or swapping it for a net doesn’t work. K. R. Cooper’s SAE paper “Pickup Truck Aerodynamics: Keep Your Tailgate Up” (2004-01-1146) found that lowering or removing the tailgate increases drag, though only by small amounts, and raises lift by up to 60%. MythBusters reached the same verdict: tailgate up was more fuel efficient. The usual explanation is that air trapped in the bed behind a raised tailgate forms a slow-moving pocket that helps the airflow pass over the bed instead of dropping into it.

Maker claims

We found no published test method behind TruXedo’s “up to 10 percent” or Tyger’s “10–13%.” Given that the controlled drag figure is 5–6% and fuel savings are a fraction of drag savings, double-digit fuel gains for a gas truck aren’t plausible as a general claim. If a maker publishes a test protocol, we’ll read it.

Why speed matters so much

Aerodynamic drag grows with the square of speed: double the speed and the drag force roughly quadruples. Around town at 30 mph, drag is a minor part of a truck’s fuel use next to acceleration, idling and stop-and-go. On a 70–75 mph interstate it’s one of the largest. That’s why every credible result above is a highway result, and why our calculator applies any improvement only to highway miles.

It also explains why results vary so much from truck to truck. Cab height, bed length, tailgate shape, ride height and tires all change how air flows over the bed, so a cover that helps one truck slightly may do nothing measurable on another. A lifted truck on all-terrain tires has bigger aerodynamic problems than an open bed.

What a small gain is worth

Small percentages translate into small dollars. Our fuel economy reality check counts only highway miles, since that’s where aerodynamics matter, and shows the savings for several scenarios. With its defaults (12,000 miles a year, 55% at highway speed, 20 mpg on the highway, $3.50 a gallon), you burn about 330 gallons a year at highway speed, and:

A high-mileage highway commuter does better, and a mostly-town truck does worse. Plug in your own numbers: run the fuel economy reality check.

If you want the best chance of a gain

The evidence says the effect is aerodynamic and mostly at highway speed, so a few things follow:

• Keep the bed covered and the cover flat. A cover that flaps or bows in the wind is unlikely to help; Car and Driver noted the Revolver X4s doesn’t flap when closed.
• Pick a low profile. Covers that sit at or near the rails, like the BAKFlip MX4, TruXedo Lo Pro or Gator soft roll-up, keep the shape closest to a covered bed.
• Keep the tailgate up. Always.
• Don’t add drag back. A loaded bed rack, crossbars or a rooftop tent will add far more drag than a cover removes.
• Watch the weight. Hard covers that publish a weight run about 61–97 lb, which matters a little in town. Soft covers are about 24–35 lb.

So why buy a cover?

For the reasons that actually hold up: keeping cargo out of sight, keeping most rain and dust out, and (with a hard cover) keeping thieves out. Our soft vs hard guide covers those trade-offs, are tonneau covers waterproof? covers sealing, and the best tonneau covers of 2026 ranks every line. If price is the deciding factor, the Gator soft roll-up is about $220 for the F-150 5.5 ft (check the price), and how much a tonneau cover costs breaks down every price range.

How we wrote this

We searched for published tests and studies of pickup bed covers, tailgates and fuel use, read each source and summarized only what it measured. Where a source measured drag rather than fuel, or an electric truck rather than a gas one, we say so. We’ll update this page if a controlled test of aftermarket covers on gas trucks is published. More on our approach at how we research.