Follow-up for more reference on costs:
Even if you somehow squeezed 10 mpg out of a loaded diesel semi, fuel is only part of the bill.
Here's what the mpg crowd leaves out:
DEF. You burn 2 to 3 gallons of it for every 100 gallons of diesel. And here in Wisconsin it freezes at 12 degrees.
Oil changes. 10 to 13 gallons of oil every time, and a shop visit runs $500 to $700.
The DPF. It fills with ash. Cleaning it is $300 to $600. Replacing it is $2,000 to $6,000.
Regens. When that filter burns off soot, you burn 3 to 8% more fuel doing it.
Emissions failures. A DEF or SCR system repair can run $4,000 to $10,000.
Idling. Close to a gallon an hour just to stay warm or cool.
And $550 a year in federal heavy vehicle tax before you even talk plates, insurance, or tires.
The trucking industry's own research group put the average cost to run a truck in 2025 at $2.34 a mile. That's the highest they've ever recorded. Take fuel out completely and it's still $1.85 a mile.
So next time somebody brags about diesel mpg, ask them what it costs per mile.
Drivers, what's the expense nobody talks about?
All the numbers are real and sourced. The cost per mile comes from ATRI's 2026 operating cost report, which covers 2025. The DEF, oil, DPF, regen, idle, and repair ranges come from truck maintenance and dispatch guides, and the $550 is the federal Form 2290 max.
Kevin’s out here talking like a diesel semi runs 10 to 14 mpg.
Bro. That’s not a truck. That’s a Prius with a sleeper.
Real loaded Class 8 numbers live closer to the mid single digits. Empty you might stretch it a little. You are not walking away with double-digit mpg like it’s a light-duty pickup.
And MPG isn’t even the whole bill.
People compare diesel to electric like fuel is the only line item. Then they forget what actually drains the wallet every month:
DEF. Burns money every fill and if you run out you’re shut down.
Oil. Big engines. Short intervals when you’re working hard.
Fuel filters. Oil filters. Air filters. They stack.
DPF and regen issues when the truck sits or idles wrong.
Coolant, belts, aftertreatment headaches that show up as downtime, not a pretty spreadsheet.
So when somebody quotes “cheap diesel miles,” ask what they left out. Fuel is loud. The fluids and filters are quiet until they aren’t.
Drivers… what’s the real mpg you’re seeing loaded, and what fluid cost hits you the most?