Ford is alleged to have rigged its heavy-duty trucks to beat emissions tests, according to a a lawsuit from a legal firm representing US drivers.

Ford's F-250 and F-350 Super Duty diesel pickups, part of the top-selling F-Series, are allegedly releasing emissions for nitrogen oxide (NOx) pollutants far in excess of the legal limit.

According to the firm's lawsuit, much like VW, GM, Fiat Chrysler and Mercedes, Ford intentionally sold its Ford F-250 and F-350 Super Duty trucks with emissions-cheating devices that mask the release of illegally high levels of NOx. As a result, consumers paid a US$8,400 premium (compared to its gasoline equivalent) for a diesel truck that is, in fact, emitting illegal levels of deadly NOx emissions.

The trucks sold from 2011 to 2017 cost US$8,400 more than their gasoline-fuelled counterparts, the filing shows.

Ford robustly rejected the allegations. "All Ford vehicles, including those with diesel engines, comply with all US EPA and CARB emissions regulations," Daniel Barbosa, a spokesman for Ford, said in an emailed statement cited by Bloomberg. "Ford vehicles do not have defeat devices. We will defend ourselves against these baseless claims."

Bosch is also accused of developing software that enabled Ford to adjust fuel levels, exhaust gas re-circulation, air pressure and urea injection rates while being tested for emissions by regulators including the Environmental Protection Agency and California Air Resources Board.

According to legal firm Hagens Berman's investigation, Ford manipulated the emissions system in affected F-250 and F-350 Super Duty trucks, in violation of federal requirements. The firm claims its independent testing revealed twice the legal limits of emissions released during normal driving.

"We believe Ford was motivated by its desire to increase sales and profits, and broke federal and state emissions laws to achieve the fuel economy, range, towing power and performance Ford promised its customers," the firm said in a statement.

Auto market intelligence
from just-auto

• Auto component fitment forecasts
• OEM & tier 1 profiles & factory finder
• Analysis of 30+ auto technologies & more