Diesel Costs $2.20 More Than Gas Now. The HD Pickup Diesel Math Just Broke

Regular gasoline fell to a national average of $3.84 a gallon on November 14, according to AAA, while diesel sat at $6.04. That is a $2.20 gap per gallon. A year ago it was 69 cents.

Here's what the headlines about cheaper gas miss: for anyone shopping a three-quarter-ton or one-ton pickup, that gap just turned the diesel option from a slow investment into a running cost. If you don't tow heavy most of the time, I think the gas V8 in the same truck is now the cheaper machine per mile, and the government's own forecast doesn't flip that back next year.

Diesel stayed near its record while gas slid

AAA's diesel record is recent: $6.5276 on September 22, 2026. Since then diesel has eased by about 49 cents, while regular gas has dropped below $4 for the first time since July. The EIA's weekly survey tells the same story with slightly different numbers: on-highway diesel averaged $6.127 on November 9, down 16.5 cents in a week but $2.29 higher than a year earlier, against $3.995 for regular. On the West Coast diesel is still $7.11.

The reasons are global rather than seasonal. EIA points to reduced refining in Russia, China and the Middle East, which pulls U.S. diesel abroad. The federal excise tax on on-highway diesel is also 6 cents a gallon higher than on gasoline, a small but permanent handicap.

Meanwhile the diesel option itself got more expensive. Chevrolet's new 8.3-liter Duramax V8, rated at 555 hp and 1,230 lb-ft, costs $11,400 over the gas 6.6-liter V8 on every 2027 Silverado 2500HD trim, according to GM Authority, citing Chevrolet's October pricing. The outgoing 6.6-liter Duramax was $9,900. Ram dealers list the Cummins at $12,995, and dealer listings put Ford's High Output Power Stroke at $12,495 on an F-250 XLT.

The mileage gap is about 20 percent. The fuel gap is 57 percent

Heavy-duty pickups are above 8,500 lb GVWR, so the EPA doesn't rate them and fueleconomy.gov has nothing to offer. The best public yardstick is Car and Driver's 75-mph highway loop. Across the 22 Ford, GM and Ram HD trucks it has run, the diesels averaged 18 mpg and the gas trucks 15 mpg. The two best diesels returned 20 mpg.

That 20 percent advantage is real. The problem is the other ratio: today a gallon of diesel costs 57 percent more than a gallon of regular. To tie a 15-mpg gas truck per mile at AAA's November 14 prices, a diesel has to deliver 23.6 mpg unloaded. None of the 22 trucks in Car and Driver's set came close.

I ran the same two averages through three price points: a year ago, today, and the EIA's November Short-Term Energy Outlook for 2027.

At 15,000 miles a year, my assumption for a truck used as a daily driver, the average diesel now costs about $1,190 more in fuel than the average gas truck. Even the best diesel in the set costs about $690 more. A year ago the average pair was a wash, and the best diesel saved roughly $250 a year.

Notice what that means for the $11,400 option. Even at last year's prices, $250 a year would have taken more than 40 years to pay it back. For unloaded driving the diesel option never paid for itself at the pump. What changed this fall is that it now costs money every mile on top of the sticker.

The Silverado makes the case against itself

Chevrolet's gas engine is the awkward data point for its own diesel. In Car and Driver's set, a 2024 Silverado 2500HD High Country with the 6.6-liter gas V8 returned 18 mpg, the only gas truck in the top 10 and level with the diesel average. A 2020 Silverado 2500HD High Country with the previous Duramax managed 19 mpg.

Those are different model years, and neither the 2027 8.3-liter diesel nor the updated 412-hp gas V8 has a published highway figure yet. But if the new pair lands anywhere near the old one, the gas truck runs about 21 cents a mile at today's prices and the diesel about 32. That is roughly $1,560 a year at 15,000 miles before you write the $11,400 check. I looked at the half-ton side of this in our earlier piece on the 2027 Silverado V8s; in the HD trucks the fuel choice matters more than the engine choice.

The case against my view

The diesel camp's answer is simple: nobody buys a Duramax or a Cummins for highway commuting. The diesel exists for weight. Car and Driver's loop is run empty, and its own editors asked for a 10,000-lb trailer to redo the test. Under a heavy load a gas V8 has to rev hard to make power, its mileage falls further than the diesel's, and the 57 percent threshold becomes reachable. Add the diesel's longer engine life, the stronger resale that diesel buyers count on, and the direction of travel: diesel fell 16.5 cents in the EIA's latest week alone.

That is a fair argument, and for someone who spends most of their miles hooked to a fifth wheel or gooseneck, I don't dispute it. But it covers only owners who actually tow heavy most of the time, and for everyone else it doesn't rescue the math. The falling price doesn't either: EIA's November outlook has diesel averaging $5.03 next year against $3.73 for gas. At that spread the average diesel still costs 3 cents a mile more, and the best one merely breaks even. EIA also raised its 2027 diesel forecast by 12 percent from October because it expects tight product markets through the end of next year. The resale premium is the strongest point on that side, and it's one I can't price from a public source; but it is a bet on future diesel buyers doing a calculation that today's buyers are losing.

What would change my mind

A sustained drop in diesel to roughly 1.2 times the gas price. With regular near $3.84, that means diesel at about $4.60. At that ratio Car and Driver's average diesel ties the average gas truck per mile, and the best ones start saving again. The EIA's weekly update on November 17 and the ones after it will show whether the slide continues or stalls.

A revised outlook. If the EIA's December 8 forecast cuts 2027 diesel to about $4.50 or less while gas holds near $3.73, the per-mile penalty disappears for the average diesel over the life of a truck ordered now. The $11,400 still wouldn't come back from fuel alone, but the diesel would stop costing extra every mile.

A published towing test, same trailer and same route, of the 2027 8.3-liter Duramax against the 6.6-liter gas V8 showing the diesel at least 57 percent more efficient under load. That would make the diesel the cheaper truck for anyone who tows regularly, not only every day.