Diesel set a record in September. Here's what it means at the dock

October 1, 2026

The number

The US average price of on-highway diesel reached $6.529 a gallon in the week of September 21, according to the Energy Information Administration. That is the highest figure since EIA started the weekly series in 1994. The old high was $5.810, set in June 2022.

A week later, on September 28, the average had slipped to $6.382. That is still about $2.63 more than a year ago.

One caveat. EIA says the September price is a record in nominal dollars, not after inflation. In real terms, 2022 was still worse.

Why diesel, and why now

EIA puts it down to tight global supply. Refining activity is down in Russia, China and the Middle East. That raises the cost of importing diesel and pulls more US diesel overseas as exports. At home, distillate inventories were about 13% below the five-year seasonal average in mid-September, which pushes refining margins up.

Gasoline has risen too, but less. The national regular average was $4.465 on September 28, up about $1.35 on the year.

What it looks like on the coast

The pain is uneven. On September 28, EIA's regional diesel averages were:

New England: $6.51
Central Atlantic (NY, NJ, PA, MD, DE): $6.53
Gulf Coast: $5.96

Those are road-pump averages. Marina fuel docks set their own prices, and the gap between two docks in the same harbor can be well over a dollar a gallon. Dock prices usually run above the road average because of lower volume, storage costs and convenience.

Where it goes from here

EIA's September outlook expects diesel to average $5.07 for all of 2026 and $4.40 in 2027, as inventories rebuild. That points to relief, but slowly, and the agency expects stocks to stay below normal into next year. Heating oil is the same product, so a cold Northeast winter would keep pressure on.

What to do on your boat

Shop the docks. Fuel-price apps and marina sites list dock prices. On a twin-diesel boat taking 200 gallons, a dollar a gallon is $200 a fill.

Run at the efficient speed. Most planing hulls burn far less fuel per mile just below or at a clean plane than at wide-open throttle. If you have a fuel flow meter, find your best gallons-per-mile RPM and use it on the run home.

Fill smart before lay-up. Diesel boats are usually stored with tanks nearly full to limit condensation. Add a stabilizer and a biocide if your engine maker approves them, and run the engine long enough to pull treated fuel through the system.

Gas boats: fill on land if you can. If your boat trailers, filling portable cans or the boat itself at a road station can save real money. Check the pump label first (see this issue's note on E15).

Keep the bottom clean. A fouled hull and a dinged prop cost fuel every hour you run. A haul-out inspection before storage tells you what you are dealing with in spring.

Diesel has come off its peak, but it is still far above last year. Plan the late-season trips with the fuel bill in mind.

Sources

eia.gov — Latest weekly US diesel $6.382 and gasoline $4.465 (28 Sep 2026); regional diesel (New England $6.510, Central Atlantic $6.531, Gulf Coast $5.955); year-on-year change
eia.gov — Weekly series history; record $6.529 week of 21 Sep 2026; June 2022 peak $5.810
eia.gov — EIA "What goes into diesel prices?" (Sep 2026): highest nominal on record, not inflation-adjusted; tight global distillate supply; inventories 13% below five-year average
eia.gov — STEO (9 Sep 2026): diesel forecast average $5.07 for 2026 and $4.40 for 2027
freightwaves.com — Trade press context on the September record and refinery outages
boatfuelprice.com — Marina fuel dock price reporting; gaps between nearby docks often $0.50 to $2.00 a gallon