Diesel Prices in the Rocky Mountain Region: Weekly Trucking Fuel Cost and Surcharge (2026)
Diesel in the Rocky Mountain region averaged $6.066 a gallon for the week of 14 September 2026, according to the Energy Information Administration's weekly survey of on-highway diesel prices. That is up 26.1 cents on the week, up $2.344 on a year earlier, and 21.9 cents below the U.S. average of $6.285.
By Small Fleet HQ | Updated
Diesel prices in the Rocky Mountain region, week of 14 September 2026
Prices are for the week of .
The figure is EIA's PADD 4 series, a volume-weighted average of cash self-serve prices with taxes included. It covers Colorado, Idaho, Montana, Utah and Wyoming.
| Measure | Rocky Mountain | U.S. average |
|---|---|---|
| This week | $6.066 | $6.285 |
| Change on the week | up 26.1 cents | up 31.8 cents |
| Change over four weeks | up 63.9 cents | up 83.1 cents |
| Same week a year earlier | $3.722 | $3.739 |
| 52-week high | $6.066, 14 September 2026 | $6.285, 14 September 2026 |
| 52-week low | $3.185, 12 January 2026 | $3.459, 12 January 2026 |
The Rocky Mountain region is the ninth most expensive of EIA's ten regions this week. Over the last 52 weeks it averaged 13.4 cents below the U.S. average. This week is the highest price in the series, which starts on 21 March 1994.
The trend in the Rocky Mountain region over two years
The chart shows the Rocky Mountain region against the U.S. average for the last 104 weeks. Move a pointer across it, or focus it and use the arrow keys, to read any week.
Fuel surcharge in the Rocky Mountain region
The calculator starts from the Rocky Mountain region's price this week. Swap in the series your contract names, then enter its base price and miles per gallon.
Enter your contract terms
How it adds up
The starting base price of $1.25 is an example, and 7.28 miles a gallon is the average ATBS reported for its owner-operator clients in 2025. On a 500-mile load, the regional and national prices give different answers:
| Contract reads | Price | Surcharge a mile | On 500 miles |
|---|---|---|---|
| Rocky Mountain price | $6.066 | $0.662 | $331.00 |
| U.S. average | $6.285 | $0.692 | $346.00 |
This week a surcharge on the U.S. average pays $15.00 more on that load than one on the Rocky Mountain region's price. The truck burns about 68.7 gallons either way, roughly $416.73 at the Rocky Mountain region's average pump price.
Diesel price before taxes in the Rocky Mountain region
Every price above includes the federal diesel tax of $0.244 a gallon and state taxes. The table takes both off the Rocky Mountain region's price for each state it covers, using the diesel columns of EIA's July 2026 (revised) tax table.
| State | State diesel tax | Taxes and fees in total | Price before taxes |
|---|---|---|---|
| Colorado | $0.205 | $0.357 | $5.465 |
| Idaho | $0.320 | $0.330 | $5.492 |
| Montana | $0.297 | $0.305 | $5.517 |
| Utah | $0.379 | $0.386 | $5.437 |
| Wyoming | $0.230 | $0.240 | $5.582 |
Wyoming has the lowest state diesel taxes in the region at $0.240 and Utah the highest at $0.386, a spread of 14.6 cents a gallon that carries straight into the price before taxes.
What EIA counts in each state's taxes and fees
- Colorado. Bridge and Tunnel Impact (BTI) Fee: $0.0700/gal, diesel only. Environmental Response Surcharge (ERS): $0.0125/gal, gasoline and diesel. Fuel Impact Reduction Fee (FIRF): $0.006125/gal, gasoline and diesel. Perfluoroalkyl and Polyfluoroalkyl Substances Fee (PFAS): $0.003125/gal, gasoline and diesel. Road Usage Fee (RUF): $0.0600/gal, gasoline and diesel.
- Idaho. Petroleum Transfer Fee (all fuels): $0.0100/gal.
- Montana. Petroleum Storage Tank Cleanup fee : $0.0075/gal on gasoline, diesel and fuel oil, aviation gasoline, and (non-military use) jet fuel.
- Utah. Environmental Assurance fee: $0.0065/gal.
- Wyoming. License Tax: $0.0100/gal.
Those state taxes are what your IFTA return settles, by the miles you run in each state. To set the Rocky Mountain region beside every other region, see diesel prices by region.
Why there is no single-state price here
EIA publishes weekly diesel averages for the country, its regions and California, and no other state. A truck fueling anywhere in Colorado, Idaho, Montana, Utah or Wyoming is inside this regional figure.
Method: how each number was obtained
- The weekly prices are EIA's PADD 4 on-highway diesel series, all types, in dollars a gallon, read from EIA's history table each day so that revisions carry over.
- EIA collects the cash self-serve price, taxes included, as of 8:00 a.m. local time each Monday.
- Federal and state diesel taxes and fees come from EIA's federal and state motor fuels tax table.
- Changes, highs and lows, gaps to the U.S. average, rank, surcharge figures and prices before taxes are our arithmetic on those figures.
The page updates only when EIA's figures change. Pages across the site follow our rating methodology.
What we could not verify
- County and local fuel taxes, and state taxes on gross or net receipts, which EIA's tax table leaves out.
- The price at any single truck stop in the Rocky Mountain region, which can sit well away from the regional average.
- The base price and fuel economy in your own surcharge program.
Sample, window and limitations
The Rocky Mountain series starts on 21 March 1994. EIA changed its survey sample on 13 June 2022 and says prices from that week on are not directly comparable with earlier weeks. The chart shows two years and the table one. The prices before taxes use this week's regional price with each state's taxes, so each is an estimate: EIA measured no price for the state itself.
How to cite this
Small Fleet HQ, "Diesel Prices in the Rocky Mountain Region: Weekly Trucking Fuel Cost and Surcharge (2026)", updated September 16, 2026, https://smallfleethq.com/fuel-cards/diesel/rocky-mountain. Price data: U.S. Energy Information Administration, weekly retail on-highway diesel prices, PADD 4, week of 14 September 2026.
Frequently asked questions
EIA's average retail on-highway diesel price for the Rocky Mountain region was $6.066 a gallon for the week of 14 September 2026, up 26.1 cents on the week before and below the U.S. average by 21.9 cents.
EIA's the Rocky Mountain region figure covers Colorado, Idaho, Montana, Utah and Wyoming.
It depends on your contract. With the Rocky Mountain region's price of $6.066, a $1.250 base price and 7.28 miles a gallon, the surcharge comes to $0.662 a mile. A contract that reads the U.S. average uses $6.285 instead, so check which series yours names.
The Rocky Mountain region's state diesel taxes and fees run from $0.240 a gallon in Wyoming to $0.386 in Utah in EIA's latest table, on top of the $0.244 federal tax.
Sources & References (6)
U.S. Energy Information Administration, Gasoline and Diesel Fuel Update, weekly retail on-highway diesel prices
eia.gov ↗U.S. Energy Information Administration, Weekly Retail Gasoline and Diesel Prices, history tables by region
eia.gov ↗U.S. Energy Information Administration, On-Highway Diesel Fuel Price Survey methodology
eia.gov ↗U.S. Energy Information Administration, definitions for retail gasoline and diesel prices, including the PADD regions
eia.gov ↗U.S. Energy Information Administration, Federal and state motor fuels taxes, July 2026 (revised) edition
eia.gov ↗Todd Dills, "Owner-op income up, with 'capacity-driven' trucking recovery ongoing, fuel-cost wildcard", Overdrive, 26 March 2026 (ATBS 2025 fuel economy)
overdriveonline.com ↗