The national average price of diesel has climbed above $6 a gallon for the first time, setting a record and rising more than 60% from a year ago.
Because diesel powers trucks, farm equipment and much of the machinery used to produce and move goods, consumers who never buy diesel are likely to feel the increase.
Higher transportation costs could push up prices for groceries, online orders and other consumer goods in the weeks and months ahead.
Consumers don't have to own a diesel-powered vehicle to be hit by record diesel fuel prices.
The national average price of diesel climbed above $6 a gallon Friday for the first time, reaching about $6.06, according to AAA data. That's up roughly 14% in just a month and more than 60% from a year ago.
The milestone follows a rapid run-up in fuel prices. AAA reported an average of $5.98 on Thursday, which at the time was already a record. A year earlier, diesel averaged about $3.71 a gallon.
The increase matters because diesel is essentially the fuel of commerce. It powers the tractor-trailers that deliver food and merchandise, as well as much of the equipment used in farming, construction and other industries.
That means the impact can spread far beyond truck stops.
Groceries could be among the first places consumers notice it
Food is especially vulnerable because it can require diesel at several points before reaching a supermarket.
Farmers use diesel-powered tractors and harvesting equipment. Food is then transported to processors, warehouses and distribution centers before finally being trucked to stores.
Refrigerated trucks carrying meat, dairy products, produce and frozen foods require additional energy.
As transportation companies face higher fuel bills, they generally try to pass at least some of those expenses to their customers. Retailers, in turn, may eventually pass them along to shoppers.
Fresh and perishable products may be particularly exposed because they frequently travel long distances and can't simply sit in a warehouse waiting for cheaper transportation.
Shipping costs could rise
Consumers could also encounter higher delivery charges.
Major parcel carriers can use fuel surcharges to compensate for increases in transportation costs. Higher diesel prices also raise the expense of moving merchandise from ports to warehouses and from distribution centers to stores.
Even products made relatively close to home may travel by truck several times before reaching a consumer.
That helps explain why a diesel price shock can eventually contribute to broader inflation.
The effect isn't necessarily immediate. Businesses operating under transportation contracts may not adjust prices until contracts are renewed or fuel surcharges change. That means some of today's diesel increase could work its way into consumer prices over the next several weeks or months.
Why diesel has become so expensive
The diesel surge is part of a broader energy squeeze stemming from disruptions to global oil and refined-fuel supplies amid the conflict involving the U.S. and Iran.
But diesel has an additional problem: supplies of distillate fuel are unusually tight.
The U.S. Energy Information Administration expects domestic distillate inventories — which include diesel — to fall below 100 million barrels and remain below their five-year range through the end of 2026 and much of 2027. EIA says reduced international refinery production and lost supplies from the Middle East, Russia and China have helped push global distillate prices higher.
EIA's latest weekly survey put U.S. on-highway diesel at $5.967 a gallon for the week ending Sept. 7, up nearly 37 cents in just one week and $2.20 higher than a year earlier. California's average was already above $7.75.
What consumers should expect
If diesel remains near current levels, consumers are most likely to see the effects gradually rather than through one dramatic price increase.
Groceries, products shipped long distances and home-delivered purchases could face the greatest pressure. Businesses that depend heavily on trucking — including retailers, manufacturers and construction companies — may also raise prices to recover some of their increased costs.
There could eventually be some relief. EIA currently forecasts retail diesel prices averaging about $5.55 a gallon during the fourth quarter and falling to around $4.40 in 2027 as oil production recovers and inventories rebuild.
However, $6 diesel currently represents another inflation risk for households. Gasoline prices determine what consumers pay when they fill up their cars. Diesel prices can help determine what they pay for almost everything else.