Diesel Hit $6.33 on Long Island. A Year Ago It Was $3.89.

A gallon of diesel in Nassau and Suffolk averaged $6.33 on Tuesday, September 15, according to the daily metro survey AAA publishes. A week earlier it was $5.99. A month earlier it was $5.64. On the same day last year it was $3.89.

That is 69 cents in a month and $2.44 in a year, an increase of about 63 percent. Regular gasoline rose too, from $3.22 a year ago to $4.42 today, but more slowly. The difference between those two climbs is where this lands on a business rather than a household.

The gap between the two fuels has nearly tripled

A year ago diesel on Long Island cost 68 cents more per gallon than regular. Today the gap is $1.91. Households mostly buy gasoline. Businesses that move things, from box trucks and dump trucks to excavators, generators and delivery vans, mostly buy diesel, and diesel is the fuel that has run furthest.

The region has not reached its peak. AAA's highest recorded Nassau-Suffolk diesel average is $6.65, set on May 20, 2022, which leaves today's price 32 cents short of the record. Long Island also sits between the statewide diesel average of $6.22 and the New York City metro figure of $6.44.

How a pump price turns into an invoice

The federal Energy Information Administration publishes a weekly average retail price for on-highway diesel. Its most recent reading, for the week of September 7, put the Central Atlantic region, which includes New York, at $6.05 a gallon, up 21 cents in a week and $2.11 from a year earlier. The national figure was $5.97, up 37 cents in a single week.

That weekly federal number matters beyond the pump because it is the benchmark trucking fuel surcharges are commonly built on, and the agency publishes guidance on calculating a surcharge from it. A surcharge pegged to the index resets when the index does. Nobody calls to renegotiate. The change shows up on the invoice.

The agency's price breakdown also shows why diesel moves on its own schedule. In May 2026, when diesel retailed nationally at $5.60 a gallon, crude oil accounted for 42 percent of the price, refining for 25 percent, distribution and marketing for 23 percent and taxes for 11 percent. For regular gasoline at $4.48, crude was 52 percent and refining 22 percent. More of what a gallon of diesel costs is decided after the oil leaves the well.

Heating season comes next

Heating oil and diesel are both distillate fuels, drawn from the same part of the barrel. Commercial buildings on Long Island that still heat with oil will be pricing this winter out of the same distillate market that carried diesel up through the summer, not the one that set last year's bills.

What it means for members

If you quote fixed prices for work that burns diesel, rebuild the fuel line in every open bid at today's $6.33, or write in a fuel adjustment clause tied to the federal weekly diesel average so the price risk moves with the price. That applies to paving, excavation, landscaping and fall cleanups, and above all to snow removal contracts priced now for a winter of diesel that has not been bought yet.

If you buy freight, pull your last three carrier invoices and find the fuel surcharge line, because it is growing whether or not your base rate does. If your building heats with oil, get quotes on both fixed and capped plans before the first cold week sets the price for you.