Diesel Just Hit a Record. Does a Diesel Pickup Still Pay Off?
At today's pump prices, a diesel three-quarter-ton needs to be 44% more efficient than its gas twin just to break even on fuel. Here's the math, and who should still pay $12,495 for it.
The national average for diesel hit $6.5276 a gallon on September 22, the highest figure AAA has on record. On September 28 it sat at $6.4709, against $4.4798 for regular gas. A year ago, diesel cost $3.6876.
That spread rewrites the oldest argument in heavy-duty trucks. If you are choosing between gas and diesel in a new three-quarter-ton, the fuel math that once leaned toward diesel now leans hard the other way. Towing is a different story, and our 2027 Silverado HD vs. Super Duty comparison covers the full spec sheets. Here, the question is money.
The Only Number That Doesn't Depend on MPG: 44%
Divide the price of diesel by the price of gas and you get the efficiency edge a diesel needs just to match a gas truck's fuel bill. At today's AAA averages, that ratio is 1.44. A diesel truck has to go about 44% farther on a gallon than the gas version before it saves a single dollar at the pump.
A year ago, the ratio was 1.18, so an 18% advantage was enough to break even. A month ago, it was 1.37. Diesel has risen 75% in 12 months, while gas is up 43%. In dollars, a gallon of diesel costs $1.99 more than regular today, compared with $0.55 more a year ago.
This ratio works for any truck and any driver, because it uses only pump prices. It also works at the state level: plug in your local AAA averages and the same division tells you your own break-even point.
Why Nobody Can Tell You the MPG
Here is the catch. There is no official fuel economy rating for a Ford F-250 or a Chevrolet Silverado 2500HD. Vehicles with a gross vehicle weight rating over 8,500 pounds, which covers heavy-duty pickups, are exempt from federal fuel economy labeling. The window sticker simply has no mpg figure.
Ford and GM don't publish their own estimates, either. GM's September 24 announcement of the new 8.3-liter Duramax lists output, towing, and braking hardware, but no fuel economy. Real-world mileage also swings widely with cab, axle ratio, tires, and above all what is hitched behind the truck.
So the table below does not use measured mpg. It uses an assumption, stated plainly, and shows what happens as the diesel's advantage grows.
The Math at $6.47 Diesel
Method: 15,000 miles a year, unloaded, a gas truck averaging an assumed 12 mpg, and AAA national averages from September 28, 2026, and September 2025. The diesel's efficiency edge is the variable. These are illustrations, not test results. The break-even percentages hold at any baseline; the dollar figures grow or shrink with it.
| Diesel efficiency edge over gas | Diesel mpg (if gas = 12) | Annual fuel: gas today | Annual fuel: diesel today | Diesel saves (today) | Diesel saves (Sept. 2025 prices) |
|---|---|---|---|---|---|
| +20% | 14.4 | $5,600 | $6,741 | −$1,141 (costs more) | $81 |
| +30% | 15.6 | $5,600 | $6,222 | −$622 (costs more) | $376 |
| +44% | 17.3 | $5,600 | $5,600 | $0 (break-even) | $731 |
| +60% | 19.2 | $5,600 | $5,055 | $544 | $1,041 |
The figures exclude diesel exhaust fluid, which modern diesel pickups consume and which adds to the diesel column. They also exclude maintenance and resale value, which vary too much by use to model honestly.
The $12,495 Question
For 2027, Ford simplified the Super Duty to two engines. The 7.3-liter gas V8, rated at 420 hp and 445 lb-ft, is standard. The only diesel is the 6.7-liter High-Output Power Stroke, at 500 hp and 1,200 lb-ft, and on an F-250 XL it adds $12,495 to a truck that starts at $45,975 before destination, according to Ford's Super Duty pricing.
Now run the payback. Even in the generous +60% scenario above, the diesel saves about $544 a year at today's prices. At that rate, fuel alone takes roughly 23 years to cover the option. At September 2025 prices, the same truck would have paid it back in about 12. At a +30% edge, the diesel never pays back on fuel at today's prices, because it costs more to run every year.
Double the miles and you double the savings or the losses. A contractor putting 30,000 miles a year on a truck that genuinely gets a large diesel advantage shortens the payback, but it's still a long wait at current prices.
Where Diesel Still Earns Its Keep
Fuel was never the whole case for diesel, and for a certain buyer it isn't the main one. The High-Output Power Stroke unlocks Ford's top ratings: up to 30,000 pounds conventional and 40,000 pounds gooseneck on properly equipped trucks. Ford's best gas towing figure is 22,500 pounds. If your trailer lives above that line, the choice is made for you.
Diesels are generally at their most efficient relative to gas engines when towing and hauling heavy loads, which is the work they're built for. Our assumed 12 mpg describes an empty truck. That's why the break-even ratio, not a single mpg figure, is the better tool: estimate your own loaded economy for both engines, then check whether the gap clears 44%.
The gas truck has an advantage of its own. Ford's maximum payload is 7,900 pounds with the gas V8 and 6,935 pounds with the diesel, since the diesel adds weight to the truck itself. For bed-heavy work such as a slide-in camper or a load of materials, gas is the stronger hauler.
What About the New Duramax?
GM's 8.3-liter Duramax, rated at 555 hp and 1,230 lb-ft, arrives in the 2027 Silverado HD and GMC Sierra HD, which are due at U.S. dealers beginning late 2026. GM's announcement says more than 60% of heavy-duty buyers choose diesel. It has not released the price of the diesel option, or of the trucks. The gas alternative is an updated 6.6-liter V8 at 412 hp and 472 lb-ft. Our breakdown of the 8.3L Duramax specs covers the engine in detail.
Until GM prices that option, the payback math for a Silverado HD can't be run. If it lands near Ford's figure, the conclusion above carries over.
What We Don't Know
- Real fuel economy for any 2027 heavy-duty pickup. There are no EPA ratings, and neither Ford nor GM publishes an estimate.
- What the 8.3L Duramax will cost as an option on the 2027 Silverado HD and Sierra HD.
- How long diesel stays near its record. Nobody can promise where pump prices go next, and the payback math moves with every swing.
- Whether Ford answers GM with new Power Stroke output or pricing.
So, Gas or Diesel?
If you tow heavy and often, especially above 22,500 pounds, buy the diesel for the capability and treat fuel as a cost of the job. That buyer was never choosing on price per gallon.
If you tow a mid-size travel trailer a few weekends a year, or mostly drive empty, the gas truck is the clear pick at today's prices. It costs $12,495 less on an F-250 XL, carries more payload, and is cheaper to fuel unless the diesel beats it by more than 44%. Stepping down a class is worth a look, too, and our F-150 vs. Silverado 1500 ownership-cost comparison runs that math.
If you're somewhere in between, divide your local diesel price by your local gas price before you sign. That one number will tell you more than any spec sheet.
