PACCAR raises DEF limp-mode speed from 5 mph to 25 mph as EPA pulls back diesel enforcement

PACCAR said on July 6 that it is pushing updated software to trucks running its MX-11 and MX-13 engines that changes what a diesel exhaust fluid fault does to the truck. The old derate floor was 5 mph. The new one is 25 mph. For an owner-operator whose DEF sensor faults a long way from a dealer, 25 mph is enough to reach an exit. 5 mph is not.

The derate floor

The derate is still there. A fault still cuts power and still has to be cleared before the truck goes back to full operation. What moves is the minimum speed the engine will allow while it is in that state. A 5 mph derate in a 70 mph lane is a safety hazard.

PACCAR is the first OEM to ship the change. FreightWaves frames the update as part of an EPA effort that has been unwinding the harshest pieces of diesel emissions enforcement since the summer of 2025. Kenworth and Peterbilt customers get it first because PACCAR builds those trucks. Other OEMs may follow with their own software, though none have said so yet.

For fuel haulers the calculation is narrow and real. A tanker stuck at 5 mph with product on board is a stranded load and a road-service call. At 25 mph it is a slow trip to a safe place to park.

Earnheart's exit

Earnheart Oil is out of the convenience business. The Oklahoma company sold its seven c-stores to Perfect Food and Gas and moved its wholesale fuels, transportation and lubricants operations to Fleet Fuels in a separate piece of the same deal.

A split sale suggests the retail sites and the wholesale book drew different buyers rather than one operator willing to take the whole thing. Watch whether more mid-size jobbers in the Southwest go the same route this year.

Crude and the Strait

Oil jumped more than 5% on Wednesday and touched a 7% gain at one point, closing at a two-week high, after Iranian attacks on Tuesday hit three commercial ships including an oil tanker and an LNG carrier. ING's analysts said Thursday that the market had been too relaxed about the U.S.-Iran deal-to-make-a-deal holding and about flows through the Strait of Hormuz staying open.

Diesel follows crude with a lag, and surcharge tables reset off a weekly benchmark, so carriers running fixed rate confirmations could absorb a few days of the move before the surcharge catches up.

What to watch

Watch whether Volvo, Daimler and Navistar publish their own derate changes. Watch whether the Wednesday crude move sticks or fades if shipping through Hormuz continues without further attacks.