What is ULSD?

ULSD stands for ultra-low sulfur diesel, diesel fuel with a sulfur content of 15 parts per million or less. It has been the only diesel sold for US highway use since the end of 2010, and it is the grade behind every diesel price this site tracks: the weekly DOE pump number, the daily spot quotes at New York Harbor and the Gulf Coast, and the NYMEX futures contract the wholesale market prices off. A quote that says ULSD is naming the same fuel a truck buys at the pump, before tax.

Where the 15 ppm limit came from

EPA began regulating diesel sulfur in 1993, when highway diesel was capped at 500 parts per million, the grade then called low-sulfur diesel. EPA's 2001 highway diesel rule cut that limit by 97 percent, from 500 to 15 parts per million, phased in from 2006, and after 2010 all highway diesel supplied to the market had to be ULSD. Nonroad, locomotive and marine diesel followed on a 2007 to 2014 schedule.

The reason was the engines. EPA's standards for 2007 and later heavy-duty trucks and buses relied on exhaust controls, such as soot traps, that are sensitive to sulfur and do not work unless the sulfur in the fuel is cut sharply. Removing it takes deeper hydrotreating at the refinery, which costs money and trims energy content slightly: EIA estimates the heat content of US distillate supply fell from about 138.6 thousand Btu a gallon in 1994 to about 137.5 thousand in 2014.

Why ULSD is the price benchmark

Three layers of the market settled on the same grade.

• The pump. Since the phase-in, on-highway diesel is ULSD, so EIA's weekly survey, the DOE number, is a ULSD price with taxes included.
• The hubs. EIA's daily spot series at New York Harbor and the Gulf Coast are quoted for ultra-low sulfur No. 2 diesel, untaxed.
• The exchange. NYMEX's New York Harbor distillate contract began as heating oil and switched to the ULSD specification starting with the May 2013 contract, per EIA. The futures market, the spot market and the pump now price the same fuel, and terminal rack prices are built on that futures and spot chain.

In the latest EIA prints, New York Harbor ULSD spot is at $4.713/gal and Gulf Coast ULSD spot is at $4.565/gal.

ULSD, heating oil and dyed diesel

Heating oil comes from the same distillate part of the barrel as diesel, which is why, as EIA notes, fall and winter heating demand affects diesel prices. Off-road diesel is usually the same ULSD with a red dye added. Under IRS rules, dyed diesel used for nontaxable purposes such as farming and off-highway business use is exempt from the federal fuel excise tax apart from a 0.1 cent a gallon leaking underground storage tank tax, and the dye marks it as untaxed. Because nonroad diesel has had to meet the same 15 ppm limit since 2014, the difference between a road gallon and a farm gallon is usually the tax, not the sulfur. Winter diesel covers the other seasonal variant, the cold-weather blend.

Worked example: reading a ULSD quote

On Monday, Sep 14, 2026, EIA's New York Harbor ULSD spot price was $5.078 a gallon. Multiplied by 42 gallons, that is $213.28 a barrel, against $102.42 for a barrel of WTI crude the same day. Gulf Coast ULSD spot was $4.946, so the harbor sat 13.2 cents over the Gulf, wider than the 7.2-cent median gap between the two hubs across the daily series this site carries.

The DOE pump number for the same Monday was $6.285, $1.339 over Gulf Coast spot. The federal diesel tax (24.4 cents) and the January 2026 average of state taxes and fees (35.86 cents, per EIA) account for about 60 cents of that gap; the rest is freight, terminal and station costs and margin. It is the same fuel at every step, priced at three points on its trip. Retail, rack and spot walks that ladder, and How do crude oil futures move diesel prices? follows it back to the barrel.

Monday Diesel reports ULSD prices as EIA publishes them and does not forecast them.