Funeral for a friend: Wave goodbye to the light-duty diesel

A Mercedes-Benz ML320 with a BlueTEC diesel engine following its debut at the 2008 New York auto show. After a long run, the diesel engine in light-duty vehicles may be coming to an end because of numerous factors.

Dearly beloved diesel fans, we are gathered here to pay our respects to the small-displacement diesel engine. It had labored breathing for some time now due to emissions scandals, tightening global regulations that drove up the costs of after-treatment devices to keep tailpipes clean, the rise of electric vehicles, and a new generation of gasoline engines that have adopted the diesel's technology.

It is very likely, I believe, that the diesel engine in light-duty vehicles -- those with less than a 8,500 gross vehicle weight rating -- will expire after the current product cycle runs its course.

Let's examine the some of the patient's vital signs as it heads to the automotive equivalent of hospice care:

Volkswagen: Emissions violations have removed the diesel engine from all of the company's U.S. vehicles. The new focus at VW is on hybrids and EVs. No more diesel-powered VWs for North America are planned.

Diesels once accounted for about 20 percent of VW's U.S. light-vehicle sales, by far the industry's highest. Other German automakers are also pushing heavily into electric or hybrid vehicles.

Volvo: The Swedish automaker likely won't offer diesel motors beyond 2023, when the company's current Drive-E engines will need to be updated or replaced to meet new environmental regs.

Mercedes-Benz: The automaker dropped plans to sell 2017 model year diesels and is weighing whether the engine has a future in North America.

Fiat Chrysler: Last week, the Justice Department sued the company, charging that the 3.0-liter EcoDiesel engine that is optional in the Ram 1500 pickup and Jeep Grand Cherokee is equipped with software that contains a defeat device. That illegal software, government lawyers claim, allows the diesel engines to emit higher levels of nitrogen oxide than legally allowed.

Europe: The diesel engine is under attack by mayors in German, French and English cities and by European Union regulators. The reason: Despite advances in emissions control systems, the engine still pollutes far more than originally believed, maybe five times as much, according to a study published last year by the British government.

Six automakers have been sued over alleged excess diesel emissions, including a new suit filed last week against GM charging that 705,000 diesel pickups from the 2011-16 model years use defeat devices to skirt U.S. emissions standards. GM denies the charges.

Major engineering changes and improvements to the gasoline engine -- downsizing and downspeeding, turbocharging and direct injection -- boost torque at low speeds, making gasoline-powered vehicles perform much like diesels. GM's 1.4-liter Ecotech four-cylinder in the Chevrolet Cruze is a good example of a gasoline engine with diesel-like performance characteristics.

None of this bodes well for diesels in light-duty vehicles after current product cycles end. By early next decade, don't be surprised if the diesel is once again available only in heavy-duty versions of pickups, such as the Ford F-250 and Ram 3500, and other heavy vehicles that are designed to haul large loads.

In an ironic twist of fate, GM, the company that drove a stake through the heart of the diesel in the late 1970s and early '80s with poorly designed V-6 and V-8 diesel motors from Oldsmobile, is the only automaker still bullish on the fuel-saving engine.

This spring, GM launched a 1.6-liter diesel engine in the Cruze compact and is now gearing up to introduce a diesel version of its top-selling crossover, the Equinox crossover. It will give GM four light-duty diesels. The midsize Chevrolet Colorado and GMC Canyon pickups offer optional diesels.

Ford, Mazda and FCA have hatched plans to offers diesels in the F-150, CX-5 and Jeep Wrangler. But with tightening global emissions standards increasing the costs to scrub tailpipe emissions of nitrogen oxide, or NOx, it may be one generation and done for these vehicles. Unless -- and it's a long shot -- a new and cleaner blend of diesel fuel becomes available that enables a diesel engine to reduce NOx emissions at the source -- in the cylinder -- and not after it leaves the engine. But oil companies have traditionally resisted forced changes to the makeup of fuels.

The diesel engine has been on life support before only to make a miraculous recovery, thanks to innovations such as selective catalytic reduction and super high-pressure fuel injection. So, the light-duty diesel's current diagnosis is a familiar one to Allen Schaeffer, executive director of the Diesel Technology Forum, a 17-year-old Washington, D.C., trade group that promotes diesel engines.

Schaeffer told me he does not see the diesel disappearing in light-duty applications. Of course, he gets paid to say things like that, but Schaeffer brings some logic to the debate:

"One of the things we are learning is that one technology does not suit all Americans' needs," Schaeffer said of the possibility that EVs will replace the internal combustion engine. "We've never been a country of one technology, and I don't think that is about to begin now."

Schaeffer says a kinder, gentler fuel could help move the light-duty diesel engine out of intensive care. "One of the things that California is recognizing now is that there are tremendous opportunities to leverage enhancements to diesel fuel," he said. "Could we imagine a future where the diesel engine wasn't running on diesel fuel, but some advanced renewable drop-in fuel? Well, it exists today. Some fleet vehicles in California have all converted their municipal service vehicles to using an advanced renewable biofuel that is 98 percent renewable."

Despite diesel's troubled outlook, sales remain strong in heavy-duty applications. In places such as Texas, farmers and ranchers almost never opt for gasoline engines in their trucks. Nissan spokesman Dan Passe says the revamped Titan, with its 5.0-liter Cummins-built V-8, is selling well, with diesels accounting for 55 percent of total U.S. sales.

Schaeffer believes engineers will develop new technology to cure the diesel's ills.

"We have faced headwinds in the diesel industry almost since time began in some way," he says. "There has never been a time when there has not been a controversy, but the technology endures."

You can reach Richard Truett at

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