With electric-car battery prices falling faster than predicted even five years ago, carmakers face tough and costly choices in choosing powertrains for the lineups in 2020 and after.
Pressed by stiff carbon-emission reduction laws in Europe and heavy regulations to encourage electric cars in China, they must assess how much to invest in new internal-combustion engines.
Added to that is the perilous position of diesels for passenger cars and light trucks in light of the VW diesel emission scandal and increasingly stiff public reaction against the technology.
For several years, carmakers have planned to offer modern turbodiesel engines as the high-efficiency powertrain in future crossover utility vehicles and pickup trucks.
The higher EPA ratings for those engines would allow them to meet corporate average fuel economy regulations adopted through 2025.
While the Trump administration is looking at freezing those rules in 2022, perhaps even rolling back the CAFE requirements, carmakers set their plans in motion years ago.
What will happen to diesels for U.S. cars + light trucks by 2025?— Green Car Reports (@GreenCarReports) July 25, 2017
The increasing uncertainty in North American regulation, public perception of diesel, and the pace of electric-car price parity all put diesel's future more up in the air than it was when the 2025 rules were adopted in 2012.
We polled our Twitter followers to see how they thought the fate of diesels for personal vehicles would play out.
It's fair to say that survey participants did not prove to be optimistic about the future of Rudolf Diesel's sparkless combustion engine in future vehicles.
By 2025, almost half of respondents (46 percent) felt that diesels would be seen "only in very low numbers."
2017 Chevrolet Cruze Diesel (with 6-speed automatic transmission), Catskill Mountains, NY, May 2017
Another 30 percent said simply, "They'll be gone" by that model year.
A further 20 percent suggested diesels would be seen not in passenger sedans and hatchbacks, but solely in SUVs and pickup trucks (likely including hugely popular crossover utilities).
CHECK OUT: Diesels Still Needed For Truck Fuel Economy Despite VW Scandal: Advocate (Feb 2016)
A mere 4 percent said diesel engines would be "offered in all new models" by 2025.
German carmakers have deep experience in diesels—including diesel pioneer Mercedes-Benz; VW Group brands Volkswagen, Audi, and Porsche; and BMW.
2014 Ram 1500 EcoDiesel, Bear Mountain, May 2014
But other carmakers have long had plans to lean on diesel as one pillar of increased fuel efficiency and reduced carbon emissions, including General Motors and Mazda.
Chevrolet and Mazda between them will have three vehicles with a diesel option on the market by next year: the Chevy Cruze compact sedan, the Chevy Equinox compact crossover utility vehicle, and the Mazda CX-5 crossover.
In an era of continuing low fuel prices, the fate of those vehicles fitted with the optional diesel engine may indicate whether our survey participants are right to be pessimistic.