| Source | Finding | Caveat |
|---|---|---|
| Car and Driver: Tesla Cybertruck range tests (2024) Steady 75 mph on a 6.6-mile oval, factory tonneau open vs closed | 58.3 kWh/100 mi with the tonneau closed vs 64.2 kWh/100 mi open, which Car and Driver sums up as about 10% more range with the cover closed. Dropping the tailgate as well changed almost nothing (64.0). | One electric truck with an integrated factory cover, at a sustained 75 mph. Gas trucks lose a smaller share of their energy to drag, and slower or mixed driving shrinks the effect. |
| Ram 1500 HFE EcoDiesel EPA rating (2015), via Car and Driver EPA highway rating of the efficiency-trim Ram, which ships with a factory tonneau | Car and Driver notes the HFE was rated 29 mpg highway with its OEM tonneau, vs 28 mpg for the standard EcoDiesel: about a 3% better rating. | The HFE had other efficiency changes, so the cover's share of that 1 mpg isn't isolated. Car and Driver says it has yet to see solid empirical data on aftermarket covers. |
| Texas Tech University, SAE paper 881874 (1988) Wind-tunnel tests of pickup drag-reduction devices, including a cover over part of the bed | A cover over the rear portion of the bed cut aerodynamic drag 5–6% and lift 30%. A cover plus a wing reduced drag about 17% on a scale model. | Drag, not fuel: at highway speed only part of a gas truck's fuel goes to overcoming drag, so the fuel saving is a fraction of the drag change. 1980s truck shapes. |
| K. R. Cooper, SAE paper 2004-01-1146 "Pickup Truck Aerodynamics: Keep Your Tailgate Up" | Removing or lowering the tailgate increases drag, though only by small amounts, and raises lift by up to 60%. | Debunks tailgate-down driving rather than measuring covers directly. |
| MythBusters: tailgate up vs down Fuel-use comparison on the same truck (official channel upload, 2025) | Tailgate up was more fuel efficient than tailgate down, busting the myth that dropping it helps. | Entertainment test on one truck; it addresses tailgates, not covers. |
| Cover makers' marketing TruXedo (Lo Pro, via etrailer) and Tyger (T5) | Claims of "up to 10%" (TruXedo) and "10–13%" (Tyger) better gas mileage. | Maker claims with no published test method. We found no independent test of a gas truck showing savings that large. |
Run the dollars for your own driving in the fuel economy reality check.
How to read the evidence
Aerodynamic drag grows with the square of speed, so any benefit from covering the bed shows up mainly on the highway; around town, weight, idling and stop-and-go dominate fuel use. The strongest controlled number we found is for drag, not fuel: Texas Tech's wind-tunnel work (SAE 881874) measured a 5–6% drag cut from covering part of the bed. Only a share of a gas truck's highway fuel goes to overcoming drag, so the fuel saving is smaller than the drag figure. The Ram 1500 HFE's EPA highway rating (29 mpg with a factory tonneau vs 28 for the regular EcoDiesel) points the same way, but that truck had other efficiency changes.
The one large result, Car and Driver's Tesla Cybertruck test, found about 10% more range at 75 mph with the factory roll-top closed (58.3 vs 64.2 kWh per 100 miles). That's an electric truck, at sustained high speed, with an integrated cover; electric trucks lose a bigger share of their energy to drag than gas trucks do. It's a useful upper bound, not a forecast for a gas F-150 with an aftermarket cover. And the old trick of dropping the tailgate makes things slightly worse, according to both the SAE "Keep Your Tailgate Up" paper and MythBusters.
A worked example
With the defaults (12,000 miles a year, 55% at highway speed, 20 mpg on the highway, $3.50 a gallon), a 2% highway improvement saves about 6.5 gallons, roughly $23 a year. Even the optimistic 5% case is about $55, so a $550 cover takes about ten years to pay for itself on fuel alone. Change the numbers to match your driving: a high-mileage highway commuter does better, a mostly-town truck does worse. The real reasons to buy a cover are in our best tonneau covers guide, and the full write-up is do tonneau covers improve gas mileage?