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What happened to diesel prices
The U.S. average retail price of on-highway diesel was $6.382 per gallon on Sept. 28, according to the EIA Gasoline and Diesel Fuel Update released Sept. 29. That is down from $6.529 a week earlier but $2.628 above a year ago, and it is the figure most carriers use to set their diesel fuel surcharge. Regional spreads are wide: California sits at $8.181 while the Gulf Coast and Lower Atlantic regions are just under $6. At the same time, freight volume is turning. The Cass Freight Index shipments component rose 2.1% year over year in August, which Cass says “ends a 42-month downturn by this measure, the longest on record.” Cass’s expenditures component climbed 18.7% year over year.
Diesel prices by region
| EIA region (Sept. 28, 2026) | Diesel, $/gal | Change vs. week ago | Gap to U.S. average |
|---|---|---|---|
| U.S. average | 6.382 | -0.147 | 0.000 |
| California | 8.181 | -0.065 | +1.799 |
| West Coast (PADD 5) | 7.357 | -0.099 | +0.975 |
| Midwest (PADD 2) | 6.526 | -0.154 | +0.144 |
| Rocky Mountain (PADD 4) | 6.407 | +0.067 | +0.025 |
| Gulf Coast (PADD 3) | 5.955 | -0.222 | -0.427 |
| Lower Atlantic (PADD 1C) | 5.953 | -0.186 | -0.429 |
Gap column is our calculation. Of the regions shown, Rocky Mountain was the only one where diesel rose on the week.
Two readings stand out. First, the weekly drop of 14.7 cents is real relief, but it only reverses part of the 24.4-cent rise from Sept. 14 ($6.285) to Sept. 21 ($6.529). Second, the West Coast premium is large enough to change lane economics: a carrier fueling in California pays $2.228 more per gallon than one fueling in the Lower Atlantic region. Shippers with West Coast origins should expect higher fuel lines than national averages suggest, even under the same surcharge table.
What the diesel fuel surcharge means for your shipment
Most LTL and truckload fuel surcharges are indexed to the weekly EIA diesel price, so a 70% year-over-year jump in diesel shows up on invoices as a much larger fuel line than shippers budgeted a year ago. With Cass showing volume and spend rising together, carriers have less reason to discount linehaul to offset fuel. The Cass Truckload Linehaul Index was 153.9 in August, up 11.3% year over year. For how fuel fits alongside linehaul, accessorials and minimum charges on a full LTL invoice, see our guide to LTL shipping costs.
Worked example (estimate from EIA prices, not an ExFreight quote)
Assume a truck averaging 6.5 miles per gallon (an assumption for illustration).
- Fuel cost per mile today: $6.382 / 6.5 = $0.98
- Fuel cost per mile a year ago: ($6.382 – $2.628) / 6.5 = $3.754 / 6.5 = $0.58
- On a 1,000-mile truckload lane: about $982 in fuel today versus $578 a year ago, a difference of roughly $404 per load
- Region matters: the same 1,000 miles priced at California’s $8.181 is about $1,259; at the Lower Atlantic’s $5.953 it is about $916
An LTL shipment pays a share of that cost through the fuel surcharge percentage, so the effect scales with your linehaul charge.
How to manage LTL fuel surcharge exposure
- Pull your last three months of freight invoices and separate linehaul from fuel surcharge to see how much of the increase is fuel.
- Check that your freight class and dimensions are accurate; a reclass adds cost on top of an already high fuel line.
- Consolidate small LTL orders where possible, and compare LTL, volume LTL and FTL for larger shipments; an LTL rate API can return those options inside your own system.
- Review accessorial charges such as liftgate or limited access, which add to the base that fuel is applied to on some tariffs.
- Recheck the EIA price each week after its Monday price date; most surcharge tables reset weekly.
To understand how density drives your base rate, see how density-based LTL pricing works.
How ExFreight can help
ExFreight’s rating engine uses density-based LTL pricing and shows LTL, volume LTL and FTL options at the same time. For trucking-only shipments ExFreight acts as a broker (FMCSA MC-677423-B). Quotes are informational and subject to change; shipments can be re-invoiced if actual details differ.
Sources
- Primary U.S. Energy Information Administration, Gasoline and Diesel Fuel Update, Sept. 29, 2026 release (prices as of Sept. 28)
- Primary Cass Information Systems, Cass Transportation Index Report, August 2026, Sept. 2026
This guide explains market and regulatory changes for shippers. It is not customs, legal or financial advice. Rates quoted are third-party index values, not ExFreight prices.
Frequently asked questions
How is an LTL fuel surcharge calculated?
Most carriers apply a percentage to the linehaul charge, set from a table keyed to the weekly U.S. average on-highway diesel price published by the EIA. When the EIA price rises, the percentage steps up the following week. Each carrier publishes its own table.
What was the U.S. diesel price this week?
The EIA's Sept. 29, 2026 release put the U.S. average on-highway diesel price at $6.382 per gallon for Sept. 28, down 14.7 cents from the prior week and $2.628 higher than a year earlier. Most carrier fuel surcharge tables reset from this weekly figure.
