Mazda brings a new diesel CX-5 SUV to the US—but why?

Enlarge / You’d have to look carefully at the CX-5’s badges to tell whether it was one of the new diesel-powered versions. (credit: Mazda)

When Mazda invited us to a roundtable discussion about powertrain technology at this year’s New York auto show, it was easy to say yes. After all, the company is responsible for a significant recent breakthrough in internal combustion engine technology. So you can imagine my surprise when it turned out the topic on Mazda’s mind was the introduction of its Skyactiv-D diesel engine to the North American market, under the hood of the (excellent) CX-5 SUV. Intrigued, I had to find out why the Japanese automaker was taking this step.

Diesel’s fall from grace

You can be forgiven for thinking that “diesel” was now a dirty word. For a while, this liquid hydrocarbon fuel looked like it might be an important tool in helping fight climate change. After all, diesel engines are much more efficient than ones that run gasoline, so you can drive further between filling stations and emit less CO2 while doing it. But CO₂ isn’t the only problematic component of diesel exhaust. A more immediate danger posed by diesel exhaust is the soup of nitrogen oxides (NOx) and particulates that result as combustion products. While CO2 will wreck our climate in the coming decades, NOx damages peoples’ lungs today. And it’s NOx that’s responsible for diesel’s fall from grace.

Or, more accurately, it’s been the widespread lying by industry to regulators about the exact amounts of NOx emissions from their cars. The most well-known culprit has been Volkswagen Group. In 2015 it got caught lying to federal regulators in the US and the penalties have been stiff. Executives have been prosecuted. Hundreds of thousands of cars have had to be bought back from owners, billions of dollars in fines were levied, and an entirely new business plan had to be created to rapidly electrify one of the three biggest car companies in the world by the middle of the next decade.