Mazda and Honda scrapped plans to introduce small diesel vehicles into the US market because of the difficulty of meeting the tough American emissions regulations, the Japanese manufacturers have told the Financial Times.

Their accounts underline how far out of line Volkswagen was with the broader car industry when it pushed ahead with bringing small diesel vehicles to the US. In the last decade, Japan’s Nissan and Korea’s Hyundai also announced but then scrapped plans to sell small diesels in the US.

The US Environmental Protection Agency announced last month that VW had admitted that starting in 2008 it had fitted 482,000 diesel vehicles sold in the US with a software “defeat device” designed to outwit emissions regulations.

The Japanese companies said that they could have adapted the diesel engines they sold in Europe to make them meet the US’s stricter standards for nitrogen oxide (NOx) emissions. But Mazda found the environmental demands made the vehicle’s performance unacceptably poor, while Honda believed the extra costs of adjusting the engines was unjustified.

Mazda’s and Honda’s struggles lend credence to the idea VW started cheating on emissions tests to overcome the difficulties of meeting US emissions standards while maintaining vehicle performance.
VW’s defeat devices turn off the vehicles’ emissions controls except when they detect the vehicle is undergoing an emissions test, meaning some vehicles emit up to 40 times permitted levels of NOx. VW has since admitted that up to 11m diesel cars worldwide feature the device.

The central challenge for carmakers has been finding a way to meet US emissions standards that does not involve treating the exhaust gases with urea to start breaking down the NOx.

Carmakers — including VW — have been reluctant to use treatment with urea on small vehicles because of the size and cost of the urea tank and the burden on owners of refilling it regularly.

Mazda in the US said it had concluded it could produce a diesel that met US standards without using urea. But, when the controls were in use, the vehicle’s acceleration and fuel economy suffered. When engineers made the vehicle drive as intended, emissions performance suffered.

“We were able to meet both our emission and our performance goals outside the US,” the company said. “But with

[US emissions] standards being as strict as they are, we couldn’t do so here.”

Honda said its Acura luxury brand considered “a few years ago” bringing a diesel-powered version of its TSX sedan to the US market, using non-urea technology. But the system would have required “some changes” to account for emissions standards in California, which are higher than those in Europe.

“We were capable of meeting the standards but the increased cost to the customer combined with the concurrent higher cost of diesel fuel negated the potential fuel economy benefit,” the company said.

VW is the only carmaker in recent years to have offered diesel cars without urea tanks for sale in the US.
VW said it could not comment on its rivals’ actions. Nissan said it scrapped plans announced in 2007 to launch a diesel-powered Maxima sedan in the US because it was focusing instead on core priorities such as electric vehicles.