Fuel and Idling in Numbers: What a Stop-and-Go Truck Burns Standing Still, and the Government Figures on Speed, Tires and Weight

Updated September 2026

Most fuel-saving advice online was measured on cars and quoted for trucks. This guide uses the figures the Department of Energy’s Argonne laboratory and EPA’s SmartWay program published for medium and heavy trucks, marks the car-only ones as car-only, and does the arithmetic at the diesel price that applied when it was written.

What idling burns

Argonne National Laboratory compiles measured idle fuel use by vehicle type. For the trucks a hauler runs:

Class 5 diesel delivery truck (19,500 lb): 0.84 gal/hour with no load, 1.11 gal/hour with accessories running
Class 6 diesel tow truck (26,000 lb): 0.59 gal/hour, 1.14 with the PTO engaged
Class 6–7 diesel, 23,000–33,000 lb: 0.44 gal/hour with no load
Class 6 gasoline, 19,700–26,000 lb: 0.84 gal/hour
Class 8 tractor: 0.64 gal/hour, 1.15 with A/C on at high idle
For contrast, a 2.0-litre car: 0.16–0.29 gal/hour

Call it half a gallon to a gallon an hour for a box or dump truck, more with the A/C or a PTO running. DOE’s work-truck fact sheet uses four hours of idling a day as its base case for utility trucks; a junk truck waiting at a curb, a dump line and a customer’s driveway can easily match that.

The arithmetic, at the $6.29 a gallon EIA reported for the week of September 14, 2026: 4 hours × 0.75 gal × $6.29 ≈ $19 a day, about $4,700 a year per truck on 250 working days. Diesel was $3.74 a year earlier, so every published dollar figure from before 2026 — including the ones in the government fact sheets — is now roughly two-thirds too low. Idle hours also count against oil changes and engine life; Argonne’s worksheet converts them to "idle miles" for maintenance for that reason.

The rule DOE gives medium-duty fleets: turn the engine off when parked or stopped for more than 10 seconds, except in traffic. Restarting costs about ten seconds of fuel.

The law on idling

Many states and cities limit idling, and the hauler, not the driver, is often the one fined. Three read at the source:

Massachusetts (M.G.L. c.90 §16A): five minutes. Up to $100 for a first offense, up to $500 after; exceptions for deliveries that need engine power and for engine-driven equipment with no alternative.
California (CARB, 13 CCR 2485): five minutes for diesel vehicles over 10,000 lb GVWR, at any location. Fines start at $300 and can reach $1,000 a day, and the owner is liable for the driver’s citation. PTO operation, traffic and servicing are exempt.
New York City (Admin. Code §24-163): three minutes, one minute next to a school, for trucks and buses, with a citizen-complaint program that pays a share of the fine to the person who filmed you.

Tires, speed, driving and weight — the truck figures

EPA’s SmartWay bulletins are written for heavy trucks; the highway ones matter less for local work, so each is labelled:

Tire pressure (any truck): 10 psi under the recommended pressure costs 0.5–1% in fuel economy; truck tires can lose up to 2 psi a month; only 8% of truck drivers check pressure with a gauge before a trip. An under-inflated tire also wears faster and is the second most common reason trucks are put out of service at roadside (see the inspections guide).
Speed (highway work): cutting highway speed by 5 mph saves about 7%; each 1 mph faster costs about 0.1 mpg. Mostly irrelevant to a truck that never sees 55.
Driving style (any truck): SmartWay puts the gain from driver training at 5% or more, with a Canadian study at 10%, and says the gains are larger for vehicles in urban service — the stop-and-go pattern where hard acceleration and braking cost the most.
Weight (heavy trucks): every 10% off the truck’s weight saves 5–10% of fuel. For a hauler the practical version is: don’t carry yesterday’s load, the spare bin or a full water tank to the next job.

Car-only figures you will see quoted for trucks: "0.2% per psi", "1% per 100 lb", "aggressive driving costs 15–30%", "$0.30 a gallon for every 5 mph over 50". All from fueleconomy.gov, all measured on passenger cars. The direction is right; the numbers are not yours.

What a truck like yours actually does

Federal Highway Administration data (2020) puts single-unit trucks in Classes 3–8 at an average of 11,893 miles a year and 7.6 mpg; DOE’s category chart has delivery trucks at 7.2 mpg and 11,600 miles a year and refuse trucks at 5.2 mpg. At 7 mpg, a truck doing 12,000 miles burns about 1,700 gallons a year moving — so four hours a day of idling can add over 40% to the fuel bill of the driving itself. Idle, not speed, is the lever for a local truck.

Routing, and what UPS actually said

"UPS saves 10 million gallons a year by never turning left" is the most-repeated routing statistic in the trade, and it is a blend of two things. UPS’s own published figure is that its routing software, ORION, deployed across about 66,000 routes, cut about 100 million miles and 10 million gallons a year — and UPS’s documents about ORION do not mention left turns. The left-turn figure is older and smaller: in 2007 a UPS spokesperson told ABC News that its "package flow" system combined with right-turn routing had saved about 28.5 million miles and 3 million gallons the previous year. We could not find that on a UPS page today.

We found no independent, published measurement of what route planning saves a small fleet. What is not in doubt: for a truck averaging 7 mpg at $6.29 a gallon, every mile of backtracking costs about 90 cents in fuel before wages and wear, and the day’s stops in a sensible order is the difference of several miles a day.

What the numbers suggest doing

Engine off at any stop over ten seconds outside traffic. The single largest saving available to a local truck, and the one with a fine attached in many places.
A gauge on every pre-trip. Two psi a month walks out of a tire; the pre-trip is the only time anyone checks.
Put the stops in order the night before, and let the driver see them in order. The saving is miles, and miles are 90 cents each.
Photograph the fuel receipt against the truck so gallons per truck per month is a number you have. The trucks that idle show up in it.
Coach the driving, not just the route. The government’s own figure is 5–10%, biggest in urban stop-and-go.

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Sources

This is general information, not legal, tax or financial advice, and RelayPoint is not a law firm, an accountant or a compliance consultant. The figures are other organisations’ published findings, read in September 2026 at the addresses listed under Sources; they describe the businesses those organisations studied, not yours, and none of them is a result of using RelayPoint.