Reports are surfacing that Stellantis has begun testing a Ram 2500 diesel truck with no modern emissions equipment — no DEF tank, no DPF filter, and no exhaust sensors choking performance. According to insiders, the test vehicle is a higher-trim model, possibly a Limited, running a pre-2008-style Cummins setup.
This development follows similar moves by Ford and General Motors, who have also been spotted running “deleted” test trucks — vehicles stripped of emissions systems — to evaluate performance and emissions under upcoming regulatory changes. Sources close to the matter say these tests align with expected EPA adjustments following the rollback of the “endangerment finding” and revisions to federal fuel standards.
If the U.S. returns to standard diesel fuel with higher lubricity — instead of today’s low-sulfur blends that damage fuel pumps — current DEF-equipped systems would likely malfunction. Automakers like Stellantis are reportedly preparing ahead, ensuring they have compliant, reliable diesel platforms ready when the rules change.
Early data from Ford’s internal tests suggest that properly tuned diesels without DEF systems can actually emit fewer pollutants than malfunctioning systems burdened with modern emissions hardware. Cleaner burn, better mileage, lower maintenance — and most importantly, more reliable power for working trucks.
The implications are massive. Should the EPA officially remove current diesel restrictions, manufacturers could release simplified, more robust diesels capable of longer warranties, stronger towing performance, and reduced failure rates. For owners tired of DEF headaches, fuel pump grenades, and DPF issues, this signals a long-awaited return to common-sense engineering.
With Ford, GM, and now Stellantis all testing emissions-free diesel prototypes, the industry appears to be bracing for an overhaul in federal fuel policy. As one insider put it, “They wouldn’t be testing these if they didn’t already know what’s coming.”
If these moves pan out, the next few years could redefine diesel performance — bringing back the durability and reliability truck buyers have missed for more than a decade.
Stay tuned — and stay petty.
