Speed Limiter for Trucks: What $6 Diesel Makes It Worth

An aftermarket speed limiter is a device fitted after the vehicle leaves the factory that stops it going faster than a speed the fleet sets. It works on the throttle signal or the fuel supply, so the cap holds however hard the driver presses the pedal. With US diesel at $6.35 a gallon, every mile driven above that cap now costs more than it ever has.

Why are fleets looking at speed limiters now?

Because fuel has nearly doubled this year. The U.S. Energy Information Administration’s weekly on-highway diesel price was $3.48 a gallon in the first week of January 2026. It reached $6.53 in the week of September 21, the highest weekly figure in a series that goes back to 1994, and stood at $6.35 in the week of October 26.

Speed is the part of the fuel bill a fleet can control. The Department of Energy’s fuel economy advice says gas mileage usually drops quickly above 50 mph, and puts the gain from observing the speed limit at 7% to 14%. For heavy trucks, the EPA’s SmartWay program says that driving at 65 mph instead of 55 mph can use up to 20% more fuel.

What does a speed limiter save a truck?

Take one truck covering 100,000 miles a year at 6 mpg, the mileage the EPA uses in its own SmartWay example. It burns about 16,670 gallons, which is about $105,900 a year at $6.35 a gallon.

An independent one-year trial of 177 vans and 30 trucks measured an average fuel saving of 5% after speed limiters were fitted (CE Delft for Novem, 2009). The fleet average is lower than the per-mile figures above, because only the fast miles change. At 5%, the same truck saves about 830 gallons, or $5,290 a year.

Fleet size	Fuel a year at $6.35	Saving at 5%
1 truck	$105,900	$5,290
10 trucks	$1.06 million	$52,900
20 trucks	$2.12 million	$105,900

Read the last row again. On these figures, a 20-truck fleet saves about the fuel bill of one whole truck every year. A fleet that runs more highway miles above its cap saves more, and one that rarely goes fast saves less. Our speed and fuel data shows how the curve bends for each vehicle type.

How does an aftermarket speed limiter work?

It sits between the accelerator and the engine. When the vehicle reaches the set speed, the limiter stops the engine being asked for more power, so the vehicle holds that speed. The driver keeps full control below the cap, and the brakes and steering are not touched.

How it does that depends on how the engine is controlled:

Vehicle	Unit	How it works
Electronic throttle (drive-by-wire)	DBW speed limiter	Works on the electronic throttle signal
Newer trucks and vans with SENT throttle sensors	SENT speed limiter	Built for the SENT digital sensor protocol
Older diesel with mechanical fuel control	System 80	Works on the fuel line
Speed limiting plus GPS tracking	TrackSpeed	Limiter and tracker in one device
Lower speeds in yards and sites	GeoKontrol 2	Speed limits by location

Any vehicle with an electronic (drive-by-wire) throttle takes the DBW limiter, so there is no model-by-model fitment list: if the pedal is electronic, it works. Older diesels with mechanical fuel control take System 80.

Is an aftermarket limiter better than the engine’s own setting?

Many heavy trucks already have a road speed setting in the engine computer, changed with the maker’s service software. If that is set and nobody changes it, it does the job for that truck. An aftermarket limiter earns its place in three cases.

Mixed fleets. Vans, pickups and older trucks often have no fleet-controlled speed setting at all. One type of limiter across the fleet gives one policy.
Control. A sealed limiter is set by the fleet owner. It does not change when a vehicle goes in for service and someone reconnects a laptop.
Proof. TrackSpeed pairs the cap with GPS tracking, so you can show where a vehicle was and that it stayed inside its limit.

For a checklist on choosing between suppliers, see our aftermarket speed limiter buyer’s guide. For more on the engine route, see speed governor for trucks: engine setting or aftermarket?.

Does it help with safety as well as fuel?

Yes, and the numbers are stark. NHTSA’s Speeding: 2024 Data counts 11,288 deaths in speeding-related crashes in 2024, 29% of everyone killed on US roads. A cap does not stop every crash, but it takes the top end off every journey your vehicles make, on every shift, whoever is driving.

Most of those deaths were not on interstates. NHTSA puts 87% of speeding-related deaths on other roads, which is why zone limits for depots, yards and town routes matter as much as a highway cap.

Is a speed limiter a legal requirement in the US?

Not for fleets. The federal proposal to require speed limiting devices on heavy trucks was withdrawn on July 24, 2025, and there is no general rule for vans or cars. Fleets that fit them do so by choice. The detail, and what states are doing for problem drivers, is in truck speed limiter law in the US.

Frequently Asked Questions

What is an aftermarket speed limiter?

A device fitted after manufacture that caps a vehicle’s top speed at a level the fleet chooses. It works on the throttle signal or the fuel supply rather than on the brakes.

How much fuel does a speed limiter save?

An independent trial of 177 vans and 30 trucks measured an average of 5% across the fleet. Per mile, the savings at high speed are bigger: the EPA says 65 mph can use up to 20% more fuel than 55 mph in a heavy truck.

How much is that worth at today’s diesel price?

For a truck covering 100,000 miles a year at 6 mpg, 5% is about 830 gallons, or $5,290 a year at the EIA’s $6.35 average for the week of October 26, 2026.

Can a speed limiter be fitted to a van or pickup?

Yes. Vans and pickups with an electronic (drive-by-wire) throttle, which is almost all modern ones, take the DBW unit, or the SENT version on newer SENT-sensor throttles.

Can drivers override it?

Not by pressing harder on the pedal. The cap is set by the fleet. Our units are sealed, and TrackSpeed reports where each vehicle went and how fast.

How do US fleets buy AutoKontrol speed limiters?

Through Scorpion, our parent group’s US team. Start with the quote form, tell us what you run, and fitting is agreed job by job, by your own technicians or our engineers and partners.

Get a price for your fleet

Diesel at $6 a gallon turns every fast mile into a line on your P&L. Tell us what you run and how many vehicles, and we will tell you which limiter fits each one and what it costs. Get a quote or book a free consultation. More on how US fleets buy is on our US speed limiters page.

AutoKontrol has made speed limiters in Britain since 1985 and supplies fleets in more than 50 countries, with approvals including ISO 9001, UTAC, TÜV and VCA.