Every so often the government does something that reaches your wallet through a document almost nobody reads.
Not a bill. Not a press conference. A notice. A few pages of emissions math posted to a website for accountants.
You have lived with the results of documents like this without noticing. The mileage rate your employer reimburses. The credit that made your neighbor’s heat pump affordable. The depreciation schedule that decided whether a freight company bought new trucks this year or ran the old ones another winter.
These notices set the price of things. They just do it two steps removed, so the connection never quite lands.
One landed this week, and the timing is what makes it worth your attention.
Diesel just set an all-time record. The national average for on-highway diesel reached $5.967 a gallon in the week ending Sept. 7, up 36.8 cents in seven days and $2.201 higher than a year earlier, according to the Energy Information Administration (EIA). The Midwest average came in at $5.946.
One day after that reading, the Internal Revenue Service (IRS) rewrote the rules for the tax credit that helps determine how much clean diesel this country produces.
Why biofuel supply decides what diesel costs you
Here is the part most fuel coverage skips.
The diesel in that national average is not all petroleum. A meaningful share is renewable diesel and biodiesel, refined from fats, oils, greases, and crop material rather than crude.
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Renewable diesel is the one that matters most, because it is chemically equivalent to petroleum diesel and runs through the same pipelines and engines at any blend level, according to the EIA. Biodiesel is chemically different and generally gets blended in at 20% or less.
That distinction sounds technical. It is the whole story, and it explains why a tax notice can move a number you see at the pump. I laid out the crude side of this equation when OPEC+ lost its grip on the oil market earlier this month.
When biofuel output falls, it does not create a niche shortage in some separate green fuel market. It punches a hole in the distillate pool, and petroleum has to fill it.
That is not a hypothetical. Renewable diesel and biodiesel consumption fell 124,000 barrels a day, or 35%, in the first half of 2025 against the same stretch of 2024.
Meanwhile, petroleum distillate consumption climbed about 170,000 barrels a day to cover the gap, according to the EIA.
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Total distillate inventories drew down 17% over that period, against a 10% average for the prior four years, based on the same analysis.
Thin inventories turn a supply disruption into a price spike rather than a rounding error. You are watching that run at full throttle right now.
What the IRS changed in the 45Z clean fuel credit
Notice 2026-53 arrived on Sept. 8. It sets the 2026 emissions rate table used to calculate the Section 45Z Clean Fcu3333el Production Credit, the federal incentive that pays producers according to how low a fuel’s lifecycle carbon intensity runs.
Here’s where the fuel market stands as this guidance lands:
- Diesel averaged $5.967 a gallon nationally in the week ending Sept. 7, an all-time high, according to the EIA.
- The previous record of $5.810 had stood since June 2022, Forbes reported.
- U.S. diesel refining margins pushed above $106 a barrel on Sept. 1, a record, according to Bloomberg.
- California averaged $7.764 a gallon, the highest of any state, the EIA confirmed.
The credit was amended and extended by the Working Families Tax Cuts, and the notice implements those statutory changes. Four of them reshape the economics.
Emissions rates must now exclude emissions attributed to indirect land use change. Eligible transportation fuel is limited to feedstocks produced or grown in the United States, Mexico, or Canada.
Negative emissions rates are prohibited outright, with one exception. And distinct emissions rates now apply to fuels made from specific animal manure feedstocks, according to the IRS.
That single exception is the tell.
What the new manure rules mean for fuel supply
Manure-derived fuel is the only category still permitted a negative emissions rate, which means the largest possible credit. The 2026 table covers dairy and swine manure, and Treasury and the IRS expect poultry and beef to join the model later this year.
The guidance also lets farm-specific manure management practices factor into the emissions math, so a producer’s actual operation counts rather than a generic assumption.
“This guidance helps unlock billions of dollars for America’s agricultural producers,” said IRS Chief Executive Officer Frank J. Bisignano, according to the IRS.
The North American feedstock limit cuts the other direction. Imported used cooking oil has become a significant input for U.S. renewable diesel plants, and restricting eligibility to three countries shrinks the qualifying pool.
I read Notice 2026-53 against the EIA’s inventory data, and the tension is hard to miss. One provision widens the supply base over years, through livestock operations that need digesters and paperwork before they produce a drop. The other narrows the feedstock pool now, in the tightest distillate market on record.
Neither shows up at your pump this month. Tax credits move refinery investment decisions, not next week’s delivery.
What record diesel prices mean for your winter budget
Here is where this stops being abstract.
Heating oil is nearly identical to diesel, drawn from the same distillate pool and competing for the same barrels. If you heat with oil in the Northeast, the record you just read about is your winter bill, not a trucking problem.
The Central Atlantic average already sits at $6.051 a gallon and New England at $5.990, according to the EIA.
Autumn harvest is the other squeeze. Combines run on diesel and grain moves on diesel, and that demand arrives every year, whether the supply is there or not. Winter heating stacks on top of it.
In my analysis, the useful move for a household is not tracking the daily average. It is recognizing that diesel is a leading indicator you can read for free. It moves before your grocery bill does, because everything on the shelf traveled to get there.
So watch two things. Whether renewable diesel output actually responds to this credit, and whether the Energy Department finishes the model updates the notice depends on before winter demand peaks.
The 45Z proposed regulations from February are still under final consideration at the IRS and Treasury Department, according to the Federal Register. Until they are finished, producers are making capital decisions against a rulebook that is not done.
A notice written for accountants is currently one of the few levers Washington has on a fuel it cannot import its way out of. That is worth knowing before the thermostat goes on.
Related: Treasury, IRS send unwelcome message on refundable tax credits
