Fuel is the line item most fleet owners want telematics to fix. It can — but the savings come from four specific behaviours, not from the device itself. Here's the arithmetic, with the government data behind it.
Idling is where most fleets find their first real money, because it is invisible on a fuel card and enormous in aggregate.
Argonne National Laboratory publishes measured idle burn rates by vehicle class. The column most people miss is the second one — consumption with accessories, PTO or hydraulics running, which is how service and utility trucks actually idle.
| Vehicle | Class | Fuel | Idle, no load | Idle, with load |
|---|---|---|---|---|
| Full-size sedan | 1 | Gas | 0.39 gal/hr | 0.59 gal/hr |
| Delivery truck | 5 | Diesel | 0.84 gal/hr | 1.11 gal/hr |
| Tow truck | 6 | Diesel | 0.59 gal/hr | 1.14 gal/hr |
| Bucket truck | 8 | Diesel | 0.90 gal/hr | 1.50 gal/hr |
| Tractor-semitrailer | 8 | Diesel | 0.64 gal/hr | 1.15 gal/hr |
Look at the bucket truck: 0.90 gallons an hour sitting still, 1.50 with the boom circuit live. That is a **67% increase**, and it is the number that applies to a utility crew parked on a job for three hours.
Source: Argonne National Laboratory idling reduction worksheet, compiling ANL, NREL, ORNL and West Virginia University measurements. The underlying measurements date from 2003–2014, so treat them as measured ranges rather than current-model figures.
Take a small utility fleet: six bucket trucks, each idling three hours a day with the boom live, 250 working days a year.
Not all of that is recoverable. Some of that idling is legitimate: the boom needs hydraulic pressure. But you cannot separate the necessary idling from the habitual idling until you can see it per vehicle, per driver, per day. That visibility is the actual product.
Diesel prices move fast, so check the current number rather than trusting ours: the EIA figure moved from $4.796 to $5.348 in the four weeks to 3 August 2026 — a 55-cent swing in a month.
The US Department of Energy puts the cost of aggressive driving — speeding, hard acceleration, hard braking — at **15–30% of fuel economy at highway speeds and 10–40% in stop-and-go traffic**.
FMCSA states there can be as much as a **35% difference in fuel consumption between a good driver and a poor driver** in the same equipment.
That 35% figure is the one worth sitting with. It means the spread inside your own fleet, between your best driver and your worst, is probably larger than any efficiency gain you could buy by replacing the trucks.
Here is the honest part, and it is the number most vendors won't show you.
The most rigorous work on this is a University of California, Davis meta-analysis pooling **17 separate studies** of onboard eco-driving feedback. Its finding: an average fuel economy improvement of **6.6%**, with a 95% confidence interval of **4.9% to 8.3%**. On a 25 mpg baseline that is about 1.7 mpg.
The same analysis found something more important: the effect **decays by roughly 0.1% per day** as drivers habituate to the feedback.
Telematics is not a set-and-forget fuel saving. The 6.6% is what you get with active use. Without ongoing coaching, refreshed metrics, benchmarking between drivers or some form of incentive, the number erodes month over month.
Any fleet buying telematics purely for fuel should budget management attention alongside the hardware. The fleets that hold their savings are the ones where somebody looks at the report every week.
For light-duty vehicles the DOE figure is concrete: **every 5 mph over 50 mph is equivalent to paying about $0.21 more per gallon.** Oak Ridge National Laboratory dynamometer testing across 74 vehicles measured an 11–13% penalty going from 50 to 60 mph and 13–15% from 60 to 70.
For heavy trucks you will often see "every 1 mph over 55 costs 0.1 mpg." We should be straight about this: that figure comes from Cummins engineering guidance, not from DOE or FMCSA. It's a reasonable OEM rule of thumb, widely repeated, but it is not a government statistic and we won't present it as one.
The fourth lever is the least glamorous and often the largest: knowing where vehicles actually went.
We install this equipment for a living, so it's worth saying plainly what telematics does not do.
It will not make a badly maintained truck efficient. Correct tire inflation is worth around 0.6% on average, up to 3%, and the right oil grade another 1–2% — those are maintenance wins, and no amount of reporting substitutes for them.
It will not fix a routing problem caused by understaffed dispatch. It will show you the problem clearly, which is not the same thing.
And it will not hold its fuel savings on its own, for the reason in the UC Davis data above.
What it will do is turn fuel from a number you see once a month on an invoice into something you can attribute to a vehicle, a driver and a day.
It depends on class and whether accessories are running. Argonne National Laboratory's measured figures put a Class 5 diesel delivery truck at 0.84 gal/hr with no load and 1.11 with load; a Class 8 bucket truck at 0.90 and 1.50; a tractor-semitrailer at 0.64 and 1.15. The "with load" column is the one that matters for service and utility fleets, because that's how they actually idle.
The most rigorous independent figure we know of is a UC Davis meta-analysis of 17 studies: 6.6% average improvement, with a 95% confidence interval of 4.9% to 8.3%. The same analysis found the effect decays about 0.1% per day without ongoing coaching. Be sceptical of anyone quoting a much larger number without saying where it came from.
No. The device produces data; the saving comes from acting on it. Fleets that review idle and driver behaviour reports weekly hold their savings. Fleets that install hardware and never open the dashboard see the effect fade, which is exactly what the UC Davis decay figure predicts.
Start with whatever idles most with accessories running, because that's where the burn rate is highest — bucket trucks, service trucks with PTO, anything with hydraulics or heavy HVAC use. Then whatever covers the most highway miles, where driver behaviour has the biggest effect. Call us and we'll help you pick the first ten.
We install GPS and telematics on everything from a single service van to several hundred trucks, at your yard rather than at a shop, so the vehicle only comes off the road for the install itself. If you want to know what your own idle number looks like before committing to a full rollout, we can start with a handful of vehicles.
Get a free quote from API Signal → or call/text 803-513-1009. We install across Georgia, South Carolina and North Carolina, and we come to your yard.
We install GPS, cameras and telematics across GA, SC & NC — at your yard, on your schedule.