Work truck gear, ranked for the people who load it every morning.
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Does a truck tool box hurt gas mileage?
A little, by two separate mechanisms, and no maker publishes a number worth repeating. Here is what changes, what it costs you, and which of the two is worth paying attention to.
Featured here: the Weather Guard 121-5-04 Aluminum Saddle Box, Low Profile, 11.0 cu ft.
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Yes, slightly, and by two separate mechanisms: the box and its contents add weight the engine has to accelerate and the brakes have to stop, and the box standing above the bed rails changes the airflow over the bed. Neither effect has a published figure we would repeat, because nobody tests tool boxes to a standard fuel economy procedure.
The honest scale: an empty aluminum crossover is a modest addition to a vehicle that already weighs several thousand pounds, and the aerodynamic change at highway speed is real but small on a shape as untidy as an open pickup bed. Loaded with tools, the weight effect becomes the larger of the two, and it is the one you control.
The weight you put in the box matters more than the box, and far more than the aerodynamics. If fuel economy is the deciding factor, buy a low-profile box and stop carrying what you do not need — in that order.
Mechanism one: weight
Weight costs fuel in city driving, where it has to be accelerated and braked repeatedly, and costs almost nothing on a steady highway cruise once it is moving. An empty crossover box is a small fraction of the truck's mass; the same box with a full set of hand tools, a cordless lineup and a few fasteners boxes in it is several times that.
This is also where the real constraint lives, and it is not fuel. Every pound in the box is a pound off your payload, and payload is a published, binding number on the vehicle certification label in the driver's door opening. The arithmetic, and where to find yours, is on how much weight can a truck bed hold.
Mechanism two: airflow
An open pickup bed is already aerodynamically poor: air spills over the cab, tumbles in the bed and drags against the tailgate. A full-height crossover box at the bulkhead changes where that tumbling starts. Depending on the truck and the box height it can smooth that region slightly or disrupt it slightly, which is precisely why a single number does not exist.
The adjacent claim — that a tonneau cover improves economy by some advertised percentage — is one this site treats as contested, because independent results point in both directions. The reasoning is on tonneau covers and gas mileage, and it applies here: be suspicious of any accessory sold on a fuel economy figure.
Two mechanisms, neither with a credible published figure.
Added weight
Changed airflow
Where it costs you
City and stop-start driving
Sustained highway speed
Size of effect
Scales directly with what you load
Small, and direction depends on the truck
Published figure exists
No
No
Can you control it
Yes — carry less
Partly — a low-profile box
Other consequence
Payload reduced by the same amount
None
What actually reduces the cost
Buy a low-profile box. A lid at or below the rail line both weighs less and sits inside the air the truck is already moving. The format is ranked on low-profile tool boxes.
Buy aluminum rather than steel if weight matters more than the last increment of security. The comparison is on aluminum against steel.
Empty the box. Most working boxes carry several items nobody has used in a year. This is the largest effect available to you and it is free.
Check your tyre pressures. A mundane point, and a bigger lever on fuel economy than any tool box decision on this page.
Low-profile and slim boxes
Four boxes that minimise both mechanisms — a lid near the rail line and a shallow front-to-back footprint — with live prices.
Weather GuardSpec-verified
Weather Guard 121-5-04 Aluminum Saddle Box, Low Profile, 11.0 cu ft
11.0 cu ft of aluminum in the low-profile saddle format that fleets have standardized on for decades. It is the box every other box gets compared with, and the reason is parts availability and a lid that stays sealed.
Build
9.7
Weather seal
9.7
Security
9.5
Bed usability
9.3
Value
8.8
Why we picked it
+11.0 cu ft published — not an estimate
+Weather Guard latch and seal hardware is available decades out
+Low profile keeps rear glass visible
+Resale value that no budget box holds
Good to know. It is the most expensive way to store tools in a pickup bed short of a drawer system. If this is a personal truck that sees a job every other weekend, the money is better spent elsewhere.
JOBOX's Gear-Lock drives multiple lock points from one key turn, which is the single biggest difference between a box a thief opens with a screwdriver and one he walks away from. The rest of the box is honest fleet-grade aluminum.
Build
9.5
Weather seal
9.4
Security
9.7
Bed usability
9.2
Value
8.9
Why we picked it
+Multi-point locking is genuinely harder to defeat than a single center latch
+Fleet-grade build with parts availability years out
+Low profile preserves rear visibility
Good to know. It costs premium money and spends it on the latch rather than the lid. If your box lives behind a locked gate every night, you are paying for security you do not need.
The narrow-body crossover. It eats noticeably less fore-aft bed length than a standard 19-20 in box, which is the whole point on a 5'5" or 5'7" bed where every inch in front of the wheel wells matters.
Build
9.1
Weather seal
9.0
Security
9.0
Bed usability
9.6
Value
9.5
Why we picked it
+Gives back several inches of bed floor versus a standard-width box
+Light enough for a one-person install
+Cheapest route into a real aluminum crossover
Good to know. If you carry long power tools in cases, the narrow body will fight you. A 19 in box swallows a circular saw case flat; this one does not.
A 69 in low-profile aluminum crossover that is only 12 in wide and 13 in tall, and — unusually for this category — states all three figures on the listing. If you are working out whether a box will clear a cover or a rear window, a published height is worth more than any amount of marketing copy about a low crown.
Build
9.2
Weather seal
9.0
Security
9.1
Bed usability
9.6
Value
9.4
Why we picked it
+Publishes length, width and height, which most of this category does not
+12 in wide leaves more usable bed floor than a standard crossover
+Paddle latches rather than a single stamped center catch
+Gloss black aluminum does not rust at the mount holes
Good to know. Twelve inches of width and thirteen of height is a genuinely shallow box. Cased power tools do not go in it, and if nothing is competing for the space above the rails you are paying for a constraint you do not have.
No. The difference between box formats is small, unmeasured, and swamped by what you choose to carry. What should decide the box is whether the lid keeps water out, whether the lock is worth anything, and whether it leaves you a usable bed — the three criteria on how much a truck tool box costs.
If you want a real fuel economy lever on a work truck, it is load discipline, tyre pressure and not carrying a rack you no longer use. A tool box is not where that battle is won or lost.
Questions people actually ask
How much mpg does a truck tool box cost you?
No credible published figure exists, because no maker tests a tool box to a standard fuel economy procedure. Mechanically there are two effects: added weight, which costs most in stop-start driving and scales with what you load, and a changed airflow path over the bed, which is small and whose direction depends on the truck and the box height.
Does a tool box affect gas mileage more than a tonneau cover?
A loaded tool box almost certainly has the larger effect, because it adds real weight while a cover adds very little. The cover's advertised aerodynamic benefit is a contested claim on this site — independent results go in both directions — so treat any accessory sold on a fuel economy number with suspicion.
Are low-profile tool boxes better for fuel economy?
Slightly, for two reasons rather than one: less material means less weight, and a lid at or below the rail line sits inside the air the truck is already disturbing instead of standing up into it. The effect is small, and it is a secondary reason to buy the format rather than the main one.
Does the weight in my tool box matter more than the box?
Yes, usually by a wide margin. An empty aluminum crossover is a small fraction of a pickup's mass; the same box loaded with hand tools, cordless kit and fasteners is several times that. It also spends your payload, which is a published and binding figure on the certification label in the driver's door opening.
Should I remove my tool box to save fuel?
Only if you are not using it. Taking a box out for a long highway trip saves a small and unquantified amount; taking out the forty pounds of tools you have not touched this year saves more and costs nothing. Carry what the work needs and leave the rest in the shop.
Last reviewed November 10, 2026. Think a figure here is wrong? Tell us at contact@toolboxandtruck.com and we will check it, fix it and date the correction — see our editorial policy.
