The DOE number and the surcharge
Do diesel prices predict freight rates?
No. Diesel is a cost the fuel surcharge passes through, and truckload rates are set by how many trucks are chasing how many loads. From February to April 2026 the DOE number's monthly average rose 48 percent while Cass's truckload linehaul index, which leaves fuel out, rose 2.7 percent.
Updated Oct 14, 2026
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No. The diesel price is a cost, and the fuel surcharge exists to pass that cost through to the shipper; the rate for the freight itself is set by how many trucks are chasing how many loads. The two sometimes move the same way, but the size and even the direction of a diesel move say very little about where linehaul rates or load counts go next.
The clean test is a freight rate with fuel taken out. Cass Information Systems publishes a Truckload Linehaul Index built from the dry van invoices it pays for large shippers, contract and spot together, with fuel and accessorial charges excluded. Set it beside the monthly average of the DOE number and the two stories come apart.
| Month | DOE diesel, monthly average | Cass linehaul index | Linehaul vs a year earlier | Cass shipments vs a year earlier |
|---|---|---|---|---|
| Jul 2021 | $3.341/gal | 147.2 | +13.4% | +15.6% |
| May 2022 | $5.571/gal | 168.6 | +13.2% | -2.7% |
| Nov 2022 | $5.255/gal | 152.1 | +1.7% | -0.4% |
| Aug 2024 | $3.700/gal | 136.7 | -3.3% | -1.9% |
| Dec 2024 | $3.494/gal | 140.7 | -0.4% | -6.5% |
| Feb 2026 | $3.722/gal | 146.3 | +2.2% | -7.2% |
| Apr 2026 | $5.501/gal | 150.2 | +5.6% | -4.4% |
| Sep 2026 | $6.291/gal | 154.8 | +10.1% | +1.9% |
Sources: diesel is the monthly average of EIA's weekly US on-highway diesel price (the DOE number) as published on this site. Cass Information Systems, Cass Indexes Historical Data (downloaded Oct 14, 2026): Cass Truckload Linehaul Index (seasonally adjusted, January 2005 = 100; excludes fuel and accessorial charges) and Cass Freight Index shipments, year over year. Cass months are the month invoices were processed.
Fuel is an input, not a rate
Diesel is one line of a carrier's cost, turned into cents per mile at the pump. The fuel surcharge is the mechanism that passes most of a fuel move through to the shipper, and that is the point of it: the linehaul rate is meant to be roughly fuel-neutral, so when diesel jumps the surcharge absorbs it rather than the base rate. If the surcharge is doing its job, the price of fuel and the rate for the freight are answering two different questions.
- US average
2022: record diesel, falling rates
In May 2022 the DOE number averaged $5.571 a gallon and the Cass linehaul index stood at 168.6, its highest reading since the index began in 2005. Diesel stayed high for months after that: every monthly average from March through November 2022 was $4.99 or more, and June's $5.753 was the peak. The linehaul index went the other way, down to 152.1 by November, 9.8 percent below its May high. It was the start of what ATRI calls the freight recession, as the capacity added in the 2021 boom outlasted demand. Expensive fuel did not hold rates up.
2024: rates turned while diesel kept falling
The linehaul index bottomed at 136.7 in August 2024, 18.9 percent under its 2022 high, and climbed to 140.7 by December. Diesel fell over the same months, from a $3.700 August average to $3.494 in December. A falling DOE number trimmed cost per mile and shrank the surcharge on every load, while the rate for the freight was already turning up. Cheap fuel was not a sign of a weak market, and it did not make one.
2026: a fuel shock and a small rate move
The 2026 run shows the difference in scale. The DOE number's monthly average went from $3.722 in February to $5.501 in April, up 48 percent in two months. The linehaul index went from 146.3 to 150.2, up 2.7 percent. By September diesel averaged $6.291, 68 percent above September 2025, while the linehaul index was 10.1 percent above a year earlier and Cass's shipments index, a count of freight moves across all modes, was up 1.9 percent. Rates did firm through 2026, after ATRI found carriers cut truck counts by 2.4 percent in 2025, the largest capacity cut since the downturn began. The rate move was a fraction of the fuel move, and freight volume barely changed.
Worked example: one 500-mile load, February to April 2026
At the site's 6.5 mpg reference, a 500-mile load burns about 77 gallons. At February 2026's $3.722 average that is $286.31 of fuel; at April's $5.501 it is $423.15, $136.84 more for the same load. That increase is what the fuel surcharge is built to carry. Over the same two months the Cass linehaul index rose 2.7 percent, about $27 on every $1,000 of linehaul. A reader who took the fuel jump as a sign that rates would jump by anything like as much would have been wrong by a wide margin. The cost per mile page runs this week's fuel figure the same way.
What actually sets the rate
Freight rates are set by capacity and demand, how many trucks are chasing how many loads. Those move on their own clock: the broader economy, retail inventories, the season, the number of carriers in the market. When trucks are plentiful and loads are scarce, rates fall no matter what diesel does. When capacity tightens, rates firm up even if fuel is cheap. Strong demand can lift diesel and rates together, as in 2021, which is why the two sometimes move in step without one driving the other.
What fuel does tell you
The DOE number is worth watching for exactly what it is: the direction and size of your fuel cost per mile, and a good read on what the surcharge line will do on the next release. That is real and it lands on the settlement. It is a cost input, not a forecast of load volume or rate per mile.
Monday Diesel reports the DOE number and translates it to the mile. It does not forecast diesel prices and it does not read the freight market.
Now look at the live data
Common questions
Do diesel prices affect freight rates?
They change what a shipper pays through the fuel surcharge, which moves with the DOE number. The linehaul rate, the price of the freight itself, is set by capacity and demand. From February to April 2026 the DOE number's monthly average rose 48 percent while the Cass Truckload Linehaul Index, which excludes fuel, rose 2.7 percent.
Why did freight rates fall in 2022 when diesel was so high?
Because capacity added during the 2021 boom outlasted demand. The Cass linehaul index fell 9.8 percent from May to November 2022 while the DOE number averaged $4.99 a gallon or more every month from March through November.
What is the Cass Truckload Linehaul Index?
A monthly index of per-mile dry van truckload linehaul rates from the freight invoices Cass Information Systems pays for large shippers, contract and spot combined, with fuel and accessorial charges excluded. It is seasonally adjusted, with January 2005 set to 100. It read 154.8 in September 2026.
Does a falling diesel price mean the freight market is weak?
No. From August to December 2024 the DOE number's monthly average fell from $3.700 to $3.494 while the Cass linehaul index rose from 136.7 to 140.7. Falling fuel trims cost per mile and the surcharge; it says little about loads or rates.
Monday Diesel reports public data and explains how this market works. It does not forecast prices, and it is not purchasing, hedging, or rate-setting advice: it never tells a reader when or where to buy fuel or what surcharge to set. Figures are attributed to their agencies as published.