US AVERAGE DIESEL COST PER GALLON 2026

As of August 17, 2026, the US national average on-highway diesel price is $5.45 per gallon, according to the EIA Weekly On-Highway Diesel Fuel Survey. This is the retail price for ultra-low sulfur diesel (ULSD) at the pump, including all federal and state taxes. After bottoming at $4.58 on July 6, weekly prices rebounded through late July and into August as renewed Strait of Hormuz tanker disruption, Russia's diesel export ban (extended in late July to run through January 2027, though refinery producers are set to resume diesel exports from September 1), and tight global refining margins lifted distillate prices.

Oklahoma has the cheapest diesel, averaging $5.00/gal as of August 18, 2026 (AAA), helped by proximity to Gulf Coast refining capacity - the largest refining complex in the US is in Texas and Louisiana - and a low 19-cent state diesel tax, well below the 74-cent Pennsylvania rate or the 102-cent California rate. Missouri ($5.04), Texas ($5.07), Kansas ($5.08), and Louisiana ($5.08) round out the five cheapest, central and Gulf Coast states near major refining and freight corridors. Texas, home to the largest US refinery complex, now ranks third-cheapest at $5.07/gal.

Diesel runs $1.40/gal above gasoline as of August 2026. Five main reasons: (1) Ultra-low sulfur diesel (ULSD) refining requires hydrotreating that removes sulfur, adding cost and reducing yield; (2) Diesel and heating oil are chemically the same middle distillate - winter heating demand competes with truck fuel; (3) Federal diesel tax is 24.4 cents vs 18.4 cents for gasoline; (4) Freight demand is global and inelastic - trucks cannot switch fuels; (5) NY Harbor distillate crack spread averaged $1.42/gal in March 2026, well above the 5-year average. See the full explainer at /diesel-vs-gas.

A Class 8 semi-truck has 200-300 gallons of fuel tank capacity (typically two 100-150 gallon saddle tanks). At the $5.26/gal national average, a complete fill of 200 gallons costs $1,052; a 300-gallon fill costs $1,578. Most owner-operators fuel strategically, topping off when prices are favorable rather than running empty. A typical fueling stop is 100-150 gallons ($526-$789 at current prices).

At cash/retail prices, major truck-stop chains (Pilot Flying J, Love's, TA Petro) are often within a few cents of regular gas stations. The real savings come with fleet cards: Comdata advertises up to 40 cents/gal at TA Petro and 10 cents at Pilot for fleets of 20 or fewer trucks, while WEX and EFS discounts are negotiated by contract and volume rather than published as a flat per-gallon rate. Without a fleet card, the price at a truck stop is typically similar to or slightly higher than a nearby gas station. Pilot Flying J's FuelFinder app shows live local prices.

Class 8 trucks average 6-8 mpg loaded on flat highways, 4-6 mpg loaded on hilly terrain or heavy loads, and 8-10 mpg empty. At 7 mpg and $5.26/gal, fuel cost per mile is 75 cents. For a 500-mile day: $376 in fuel. At 6 mpg (loaded, hilly): $438 for 500 miles. Use the fleet calculator at /fleet-fuel-calculator for your specific vehicle and route.

For over-the-road truckers using multiple chains, Comdata typically offers the best discount - its advertised rates are up to 40 cents/gal at TA Petro, 10 cents at Pilot and 8 cents at Love's (for fleets of 20 or fewer trucks; larger fleets negotiate custom pricing). For owner-operators: EFS Fleet Card (WEX) discounts are negotiated by contract rather than published as a flat rate. For chain-loyal drivers: Pilot Pro Card at Pilot locations, Love's Express Card at Love's. For mixed fleets: WEX Fleet Card offers the most granular spending controls. See the full comparison at /fleet-fuel-cards.

EIA's August 2026 Short-Term Energy Outlook (published August 11) projects retail diesel will average $4.85/gal for full-year 2026 and about $4.07/gal in 2027 as global refinery capacity grows and crude oil prices fall. The August outlook is the first to incorporate the mid-July price surge, revising the full-year 2026 figure up from the $4.61 the July STEO had projected before the rebound. That surge unfolded through late July: after bottoming at $4.58/gal on July 6, the weekly national average climbed to $4.80 on July 13, $5.13 on July 20, $5.31 on July 27, and peaked at $5.35 on August 3 before easing to $5.26 on August 10 - still above the STEO's full-year path - as renewed Strait of Hormuz tanker disruption, Russia's diesel export ban (extended in late July through January 2027, with refinery producers set to resume exports September 1), and tight global refining margins pushed distillate prices up. The full-year $4.85 average sits below the current weekly reading because prices ran well under $4.85 through the first half of 2026.