Truck Fuel Consumption CalculatorEvery Gallon, Priced.
Real miles per gallon for your truck, your load, your speed and your idle hours. Fuel and DEF for the trip and the year, the CO2 that goes with it, and the fixes ranked by what each one actually saves you.
The truck and the trip
Pick a truck type for a baseline, or type the MPG you actually see.Idle, prices and the year
Idle is counted in gallons per hour. DEF is priced on its own.This trip
This year
Same truck, same habits, for the miles you entered.What each fix is worth
Annual saving for one change, against the setup entered.An estimate from published rules of thumb and the numbers you entered; your fuel receipts are the truth. If the truck runs well below what this says it should, something on the truck is burning the difference.
Baseline, Adjust, Then Add The Idle.
No percentage of a percentage. The truck starts at a real MPG, each condition scales it, idle fuel is added by the hour, and DEF rides on top. Every figure below is live.
Factors used: loaded 1.00, partial 1.08, empty 1.18; flat 1.00, rolling 0.94, mountain 0.86; mild 1.00, cold 0.95, hot 0.98; tires at pressure 1.00, worn 0.97, low rolling resistance 1.03; no aero 1.00, skirts 1.05, full package 1.07. The speed term is the industry rule of thumb of about 0.1 mpg per mile per hour, applied either side of the 62 mph cruise the baselines are quoted at, capped at 20 mph over.
DEF is a percent of those gallons at its own price. CO2 is gallons times 22.4 lb, the EPA factor for diesel (10.21 kg per gallon). Annual figures use the same economy for your yearly miles and your idle days.
- Adjust the baseline
- Count the gallons
- Price it and weigh it
- Rank the fixes
Each rung in the ladder re-runs the year with one thing changed, speed down 5 mph, idle down an hour, better tires, more aero, 10% fewer miles, and reports the difference in dollars.
What A Truck Should Be Getting.
Published figures from the people who measure fleets for a living. If your truck is well under them, the fix is in the shop, not in the driver's seat.
The loaded, mixed-fleet national average across roughly 1.7 million tractors. The calculator's Class 8 sleeper default sits at the bottom of that range on purpose.
What fleets running newer aero tractors, low rolling resistance tires and trained drivers averaged in the North American Council for Freight Efficiency's 2024 Fleet Fuel Study. The gap to the national average is the opportunity.
A Class 8 engine at low idle with light accessory load. With air conditioning, a block heater load or a PTO it climbs to 1 to 1.5 gal/h. A 10-hour rest-stop idle is 8 gallons.
What an SCR aftertreatment system injects relative to the diesel burned. A truck through 150 gallons a day uses 4 to 7 gallons of DEF, priced separately from fuel on every invoice.
The EPA emission factor for diesel, 10.21 kg of CO2 per gallon. It is the figure behind every fleet carbon report, and it is what the calculator's CO2 line uses.
Air drag grows with the square of speed, so the last five miles an hour are the most expensive five. Governing at 65 instead of 70 on a 6.5 mpg truck is roughly half a mile per gallon.
Fuel Is The Biggest Line. Here Are The Others.
The Fuel Economy Problems A Shop Fixes.
A DPF that regenerates every day, a boost leak, dragging brakes, an axle out of line: none of them show up in a driving habit. If the receipts say the truck is a mile per gallon under what it should be, bring it to Bishop Lane.
MPG, Idle, DEF And Where The Fuel Goes.
(502) 789-6644How many miles per gallon does a semi truck get?
A loaded Class 8 tractor-trailer averages about 6.5 to 7 mpg across the US fleet. Fleets that take part in the North American Council for Freight Efficiency's annual study, which run newer aerodynamic trucks with trained drivers, averaged 7.77 mpg in the 2024 study year. A pre-2010 tractor without aero parts can run under 6, and an empty truck gets 10 to 20 percent better than a loaded one.
How much fuel does a semi truck burn idling?
About 0.8 gallons an hour at low idle with light accessory load, and up to 1 to 1.5 gallons an hour running air conditioning or a heavy electrical load, according to US Department of Energy figures. Ten hours of idling a night at 0.8 gal/hr is 8 gallons, about 30 dollars a night at today's prices, before the engine wear.
How much does speed affect truck fuel economy?
The industry rule of thumb is that every mile per hour above 55 costs about 0.1 mpg, because air drag rises with the square of speed. Running 70 instead of 65 on a 6.5 mpg truck costs roughly half a mile per gallon, which over 110,000 miles a year is more than 1,200 gallons.
How much DEF does a truck use per gallon of diesel?
Diesel exhaust fluid consumption is typically 2 to 5 percent of diesel use, with about 3 percent a reasonable planning figure for a modern SCR engine. A truck burning 150 gallons of diesel a day uses roughly 4 to 7 gallons of DEF. The calculator prices DEF separately so the cost shows up where it belongs.
How much CO2 does a gallon of diesel produce?
Burning one gallon of diesel releases about 22.4 pounds (10.21 kg) of carbon dioxide, the US Environmental Protection Agency's emission factor. A truck using 17,000 gallons a year emits about 190 tons of CO2, so every gallon saved counts twice, once at the pump and once in the air.
Do trailer skirts and tails really save fuel?
Yes, at highway speed. Trailer side skirts are generally credited with 4 to 5 percent, and a full package with skirts, a tail and a gap reducer with 6 to 8 percent, in highway operation. The saving shrinks in city and regional work where the truck spends less time at speed, which is why the calculator asks for your terrain and speed.
Why does my truck's fuel economy drop in winter?
Cold, dense air adds drag, winter diesel blends carry a little less energy, engines take longer to reach operating temperature, and idling for cab heat climbs. A 5 percent winter penalty is typical and the calculator's cold-weather setting applies it; the idle hours you enter are usually the bigger number.
What is the best way to improve a semi truck's fuel economy?
In most cases, in this order: slow down on the highway, cut idle time with an APU or bunk heater, keep tires at pressure and move to low rolling resistance tires, add trailer aerodynamics, and keep the engine healthy, meaning clean air and fuel filters, a working aftertreatment system and no boost leaks. The calculator's savings ladder ranks the first four for your own numbers.
Can a mechanical problem hurt fuel economy?
Yes, and it is the one the calculator cannot see. A clogged DPF that keeps regenerating, an EGR fault, a boost leak, dragging brakes, misaligned axles and worn injectors all burn fuel with no change in the way the truck is driven. If the truck's real numbers are well below what the calculator says they should be, something on the truck is wrong.
Does Superior work on fuel economy problems?
Yes. Superior Truck and Trailer in Louisville handles the mechanical side of fuel economy: EGR & DPF service, Performance ECM Tuning, Preventative Maintenance, Truck & Trailer Alignment and Tire Repair, at the shop on Bishop Lane or with a mobile service truck.
Burning More Than The Math Says?
Regens every day, a truck that will not pull like it used to, receipts a mile per gallon under the fleet. Call the shop on Bishop Lane, 24 hours a day, and a person answers.
(502) 789-6644