Speed limiter impact calculator
Enter your current cruise speed and a governed speed, your weekly miles and how many of them are at highway speed, plus your rate per mile, fuel economy and diesel price. The calculator shows how much extra driving time the lower speed takes, how many miles and dollars you could lose if hours are your limit, and how much fuel you'd save.
YOUR NUMBERS · defaults are EXAMPLES, replace them
EPA rule of thumb: about 0.1.
Fuel saved per week$53
- Extra driving time for the same miles
- 81 min
- Miles lost if your hours are the limit
- 88 mi
- Revenue at risk on those miles
- $203
- Fuel economy at governed speed
- 6.8 mpg
- Fuel per highway mile, now vs governed
- $0.60 vs $0.57
Hours lost = highway miles / governed speed - highway miles / current speed. Miles lost = highway miles x (1 - governed / current). Governed mpg = mpg + 0.1 x mph slower.
Running 65 mph? We plan loads and appointments around your real speed, so the schedule works before you say yes.
Get loads planned for my speedBy Evan DavidsonUpdated Sources checked
Is there a federal speed limiter rule?
No. A 2016 proposal from FMCSA and NHTSA would have required speed limiting devices on heavy vehicles rated over 26,000 lb, and FMCSA followed it with a 2022 notice. Both were withdrawn on July 24, 2025 Parts and Accessories Necessary for Safe Operation; Speed Limiting Devices: Withdrawal (2025-13928)Federal Register (FMCSA and NHTSA), 2025. Checked 2026-10-11.Open the source. As of October 2026, no federal speed limiter requirement is in effect. Carriers can still govern their own trucks, and leases can require it.
How the calculator works
A lower top speed has two effects that pull in opposite directions: it costs time and it saves fuel. The calculator measures both on the miles you drive at highway cruise, since city and stop-and-go miles don't change much.
- Highway miles = weekly miles x the share at cruise speed.
- Extra time = highway miles / governed speed - highway miles / current speed.
- Miles lost = highway miles x (1 - governed / current). This only happens when your driving hours are the limit, so you can't make the time up.
- Revenue at risk = miles lost x your rate per mile.
- Fuel saved compares gallons at your current mpg with gallons at the governed speed's mpg. EPA's rule of thumb is about 0.1 mpg for each mph slower Reducing Highway Speed (EPA-420-F-16-029)U.S. EPA SmartWay, 2016. Checked 2026-10-11.Open the source; you can change it.
A worked example
A driver runs 2,500 miles a week, 80% at a 68 mph cruise, and is weighing a governor at 65 mph. They earn $2.30 a mile, get 6.5 mpg and pay $3.90 for diesel.
- Highway miles (80% of 2,500)
- 2,000 mi
- Extra driving time
- about 81 min
- Miles lost if hours are the limit
- 88 mi
- Revenue at risk (88 x $2.30)
- $203
- Fuel economy at 65 mph
- 6.8 mpg
- Fuel saved (307.7 vs 294.1 gal)
- $53
If appointments, not hours, set the pace, the time cost is small and the $53 is a clear saving.
What the result means
The answer depends on what limits your week. If your hours-of-service clocks end most days, the governed speed costs real miles, and revenue at risk will usually be bigger than the fuel saved. If dock waits, appointments and traffic set your pace, you rarely use your full hours, the extra minutes fit inside the slack, and the fuel saved is mostly money in your pocket.
Most weeks are a mix. Use your own numbers and try a few speeds. The hours of service calculator shows how close you run to your limits, and the truck driver schedule guide explains how those limits shape a week.
Speed, fuel and money
Fuel economy drops as speed rises because air resistance grows quickly with speed. A truck with good aerodynamics loses less; a boxy load or an open deck loses more. To see what a run costs in fuel at different speeds, use the trip fuel cost calculator, and plan where to fuel with the semi truck fill-up cost calculator.
Curious how fast semis can really go when nobody governs them? Our guide to the fastest semi truck compares record runs with everyday fleet speeds.
Setting a governor on your own truck
On most modern trucks, the top speed is a setting in the engine's electronic controls, so changing it is usually a quick job for a dealer or a shop with the right software. Some owners set the road speed limit a little above their usual cruise and use cruise control for the rest. Others set a lower limit and pair it with a higher cruise-control limit for passing on hills.
Before you change anything, check your lease or carrier agreement, which may set a limit for you, and talk to your insurer, since some policies reward lower governed speeds. Then try the new speed for a few weeks and compare real fill-ups. Your own receipts will show the fuel saving better than any rule of thumb.
When time matters most
Some freight pays for speed: time-critical loads and long runs where every hour counts. Teams cover more miles without either driver breaking the hours limits, which makes a governed speed easier to live with. For teams, team driver dispatch explains how we plan long, time-sensitive runs around two drivers' hours.
Sources: Federal Register, Parts and Accessories Necessary for Safe Operation; Speed Limiting Devices: Withdrawal (2025-13928) (2025); U.S. EPA SmartWay, Reducing Highway Speed (EPA-420-F-16-029) (2016).
Questions about this tool
CH 01Is there a federal speed limiter rule for trucks?
No. FMCSA and NHTSA proposed a rule in 2016 that would have required speed limiting devices on heavy vehicles, and FMCSA issued a follow-up notice in 2022. Both were withdrawn on July 24, 2025. Many carriers still govern their trucks by company policy, and lease agreements or insurance terms can set limits, but no federal speed limiter requirement is in effect.
CH 02How much fuel does driving slower save?
EPA's rule of thumb is about 0.1 mpg gained for each mph slower, though the real effect depends on the truck's aerodynamics, gearing, load and conditions. At highway speeds, wind resistance grows quickly, so the savings are biggest at the top end. Log your own fill-ups at different speeds to find your truck's number.
CH 03Do speed limiters cost owner-operators money?
They can, when driving hours are the limit. If the hours-of-service clocks end your day, a lower top speed means fewer miles in those hours and less revenue. If appointments, traffic or dock waits set your pace instead, a lower speed costs little time and saves fuel. The calculator shows both the time cost and the fuel saving.
CH 04What speed are most company trucks governed at?
It varies by carrier, and there's no official national figure. Settings depend on each company's safety policy, fuel goals, insurance and driver recruiting. If you're leased to a carrier, your lease or the carrier's policy will say. If you run your own authority, the setting is your choice within posted limits.
CH 05Does driving slower reduce wear on the truck?
Generally yes. Lower speeds put less load on the engine, tires and brakes, and EPA notes reduced highway speed can help extend their life. Lower speeds also give more time and distance to react and stop, which matters for safety and for insurance. These benefits are harder to put in dollars, so the calculator leaves them out.
Loads planned for your real speed
We plan appointments and reloads around how fast your truck really runs. Every load waits for your yes, and the rate con comes straight to you.