It's been 80 years since the first Mercedes-Benz diesel vehicle went into volume production.
Over that time, German makers have developed, refined, and promoted the combustion-ignition engine as a more fuel-efficient method of powering personal vehicles.
Followed by Volkswagen Group's various makes, BMW, and the rest of Europe's car industry, diesels surged to roughly half of all the new cars sold in Europe—and held their value better than gasoline cars.
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Then, last September, came the Volkswagen diesel emission scandal.
Combined with efforts by Paris to ban earlier diesels with few emission controls from entering the city, the spreading scandal has thrown a cloud over the public perceptions of diesel vehicles worldwide.
Is the end now in sight for diesel passenger cars from the big German makers?
2012 Volkswagen Passat TDI Six-Month Road Test
That seems at least a possibility.
The new Volkswagen Group strategic plan, issued this month, includes a pledge to launch no fewer than 30 different battery-electric vehicles over the next 10 years.
That could be viewed as either a belated acknowledgement that customer demand for long-range electric vehicles does in fact exist, or simply cover for continuing to produce cars with combustion engines for the foreseeable future.
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But there are some other ominous signs on the horizon.
For one, Germany plans to require that all new passenger vehicles registered in the country by 2030 be zero-emission—whether powered by batteries or hydrogen fuel cells.
India has put forward a similar plan, though whether either technology will provide cars in the $8,000-to-$10,000 price range even then remains to be seen (let alone the challenges of a hydrogen fueling infrastructure in India).
Audi of America president Scott Keogh with Audi e-Tron Quattro Concept, 2015 Los Angeles Auto Show
And it's already clear that European luxury brands, caught off-guard by the sales success of the unlikely Tesla Model S, are scrambling to launch their own luxurious, fast, long-range electric cars.
Audi will launch its Q6 e-tron in 2018; BMW has a 200-mile i5 crossover SUV in the works; Mercedes plans no fewer than four electric cars by 2020, two sedans and two SUVs; Jaguar will have an all-electric F-Pace; and so forth.
Still, it's far too earlier to write off diesel cars just yet.
For one thing, European makers desperately need diesels—regardless of what it will take to get them through new and tougher real-world emissions testing—to meet increasingly tough short-term European Union limits on carbon emissions from motor vehicles.
Plug-in hybrids will take them part of the way there, but it's virtually impossible to switch the mix of engines from 50-50 diesel and gasoline to mostly gasoline overnight.
2015 Ram 1500 EcoDiesel HFE
Similar rules in North America will likely boost the percentages of diesel engines in the large SUVs and pickup trucks sold in that market between now and 2025.
And Mercedes-Benz, for one, hasn't even considered walking away from diesel.
The Canadian outlet Auto123, in a review of the Mercedes technology strategy, notes that the company plans to keep combustion engines as a core part of its lineup for at least "several decades," in the words of a company executive.
It will make them increasingly fuel-efficient, using 48-volt enhanced start-stop systems and other advanced technologies to reduce their fuel consumption.
But it remains early days yet for battery-electric vehicles.
2015 Mercedes-Benz GLK Class (GLK250 BlueTEC)
As writer Benjamin Hunting notes:
Mercedes-Benz isn't about to walk away from a hundred years of automotive development on a whim, and its assessment of the transportation realities facing most drivers in the coming decades is level-headed and grounded in a development pace the company understands quite well.
So we'd suggest that while diesel may represent a powertrain technology that has little future growth and is more likely to shrink, it's premature to write its obituary just yet.
Unless, of course, customers simply stop buying them.