The makers of plug-in hybrids and E.V.'s have reaped billions of dollars in federal loans and energy grants. Buyers of the electrically enabled vehicles have also been given bountiful perks, from tax credits and the privilege of high-occupancy vehicle lanes to home charging units underwritten by taxpayers.
Yet vehicles that were once the antithesis of eco-friendly are making far deeper inroads with mainstream consumers: fuel-sipping, ultralong-range diesel cars.
Attracted by newly quiet and clean-running engines that deliver some 15 to 30 percent better mileage than their gasoline counterparts, Americans flocked to diesels in 2012. Sales of diesel passenger cars and S.U.V.'s jumped by nearly 26 percent from 2011. That's despite the stubbornly high price of diesel fuel that, at $3.87 a gallon on average, is 23 cents more than regular gas (but a penny less than premium grade).
Given that reality, some automakers are wondering out loud why new-school diesel cars -- which in some cases burn even less fuel and produce lower levels of global-warming gases than hybrids -- are getting no love or largess from Washington.
"This planet will not be rescued by superexpensive technology for the few, but when the majority of mobility is clean," said Rainer Michel, vice president for product planning at Volkswagen of America. "Diesel is far less expensive than plug-ins and E.V.'s, with better range and performance. This technology is available today."
That assessment might be expected from VW or another automaker based in Europe, where roughly half of all new cars are frugal diesels. One in five new VWs sold in the United States today is diesel-powered, making the company by far the nation's leader.
But with automakers on a steep climb to the federal fuel economy target of 54.5 m.pg. for 2025, even domestic automakers can no longer afford to ignore a technology with so much potential.
For instance, the new Chevrolet Cruze Diesel, carrying a 46-m.p.g. federal highway rating, is officially the highest-mileage nonhybrid sold in America. The Mazda 6 Skyactiv-D sedan goes on sale this year. A Cadillac ATS diesel is in the works.
The Jeep Grand Cherokee EcoDiesel, powered by a turbo V-6 with Fiat connections, is arriving in dealers. Jeep executives may expand that engine's availability, perhaps to the all-new 2014 Cherokee or a 2015 Wrangler. Ford's Transit commercial van will also get diesel power.
Despite remarkable advances in mainstream gasoline engines, the combustion cycle developed by Rudolf Diesel at the end of the 19th century continues to be more fuel-efficient. For one, diesel engines squeeze the air in their cylinders to such pressures that the injected fuel ignites with no need for an electric spark. And gallon-for-gallon, diesel fuel contains some 12 percent more energy than gasoline. The upshot: diesels consume about 15 to 30 percent less fuel over all.
Owners of heavy-duty pickups have long relied on these durable, hard-working engines, which have the reputation for running 300,000 miles and more. This fall, the 2014 Ram -- among the mileage leaders on the gasoline side -- will become the only light-duty pickup to offer a diesel, a 3-liter V-6 shared with Jeep. That innovation, in a pickup class that accounts for more than a million sales each year, is sure to be closely watched by Ford and Chevy.
About 6.7 million diesel vehicles were on American roads in 2012, according to R. L. Polk registration data, but barely 800,000 of those were passenger cars and S.U.V.'s; heavy-duty pickups and vans account for most of the remainder. That compares with 2.3 million registered hybrid models.
The number of available diesel car and S.U.V. models is expected to double by the end of 2014, to 34 from 17, according to the Diesel Technology Forum.
An industry analysis firm, LMC Automotive, projects that diesel market share will double by 2018, from 3.7 percent to 7.5 percent. That would rival the 8.7 percent for all hybrids and plug-ins combined. And battery-only E.V.'s? They're expected to capture just 0.6 percent of sales.
The Germans are going all out. New Bluetec versions of the GLK-Class crossover and C-Class sedan will give Mercedes-Benz eight diesel models in its 2014 American lineup, including the E250 Bluetec, a 4-cylinder version of the E-Class sedan.
BMW will drop a 4-cylinder turbodiesel capable of 45 m.p.g. highway in its 2014 328d sedan and xDrive Sports Wagon in August, joining the X5 xDrive 35d S.U.V. and 535d midsize sedan in showrooms. Porsche, too, offers a diesel, in the Cayenne S.U.V.
VW foresees increasing diesel sales to at least 30 percent of its total American sales. Within three years, Audi hopes to roughly triple its American diesel penetration, to nearly one in five sales. Like Audi, VW has publicly committed to offering a TDI diesel option for all of its mainstream models. The A8 TDI luxury sedan has joined the Q7 TDI S.U.V. in showrooms. This summer brings TDI versions of the Q5 crossover, A6 sedan and A7 premium hatchback. A new A3 TDI comes early next year.
The fuel economy edge of diesel vehicles is most notable at higher speeds, making them a wise choice for Americans who commute long distances on highways. Hybrids, in contrast, shine in urban and suburban driving, where battery power and regenerative braking help them beat diesel mileage by a wide margin. But in terms of driving enjoyment, it's no contest: diesels, with their powerful surge of low-end torque, make typical hybrids feel slow and spiritless in comparison.
In widely publicized cases, the real-world mileage numbers of some hybrids have been a disappointment. Owners of the Ford C-Max and Fusion Hybrid have filed class-action lawsuits over window-sticker ratings that proved overblown. That has focused attention on the E.P.A.'s testing regime, which seems to credit hybrids for illusory mileage while understating diesel efficiency.
"You'll never find a diesel driver complaining that they're not getting the posted mileage," said Allen Schaeffer, executive director of the Diesel Technology Forum. "They all brag that they're doing better."
Such pleasant surprises have been borne out in my own testing. Several VW car models can achieve 50 highway m.p.g., whipping their 40- to 43-m.p.g. federal ratings. The Chevy Cruze Diesel showed 49 highway m.p.g., beating its 46 m.p.g. estimate. The Mercedes GLK 250 Bluetec, rated at 33 m.p.g. highway, returned 37.
Notably, diesels do their thing without the hassle or inconvenience of hybridlike driving tricks, including obsessively avoiding the gas pedal.
"You don't have to drive gingerly," said Doug Skorupski, manager of technical strategy for VW of America. "You can drive normally and still get big numbers."
The limo-size Audi A8 TDI sedan, in my testing, delivered 39 m.p.g. even at a 70-m.p.h. cruise, 3 m.p.g. above its estimate.
Diesels, analysts add, also pay back owners with higher resale values than comparable gas models, and with driving ranges that read like misprints.
The Audi A8 TDI can cover more than 800 highway miles, enough to drive from Chicago to New York without stopping for fuel. (Don't try that in an E.V.). Chevy's Cruze can top 700 miles. A clever VW television ad shows two friends learning to speak Spanish fluently in the 13 hours and nearly 800 miles it takes to drain the Passat TDI's tank.
One long-held assumption -- that Americans have bad memories of dirty, smoky, unreliable diesels of the '70s and '80s -- isn't supported by current research, automakers say. Most consumers are decades removed from diesel's Dark Ages.
"Younger buyers, especially, don't have those notions of what diesel was like," said Wayne Killen, general manager of product strategy for Audi of America.
The real barriers include unpredictable diesel prices, concerns over convenient access to filling stations and unfamiliarity with the technology. Diesel, Mr. Killen said, is still below the radar for many mainstream shoppers, even those seeking better mileage.
Yet many objections are being washed away. About 52 percent of America's gas stations now have at least one diesel pump. The technology, said Mike Omotoso, an LMC Automotive analyst, adds roughly $1,500 to $3,000 to the price of a gasoline car, but the gap is shrinking.
The clattering noise and visible pollution of primitive diesels is history. Many models carry multigallon tanks of urea, a liquid that produces ammonia to scrub smog-forming nitrogen oxides from the exhaust. Clean diesels have adopted filters to trap microscopic particles that can be carcinogenic.
Though gasoline direct-injection engines have improved markedly, engineers say they may actually face tougher hurdles to meet future pollution standards. While diesel cylinder pressures are declining, direct injection engines are going the other way to enhance efficiency -- akin to how diesels traditionally work, which could create a new round of emissions challenges.
Fuel strategies aside, executives of German brands welcome competition from America and Japan, saying the diesel tide will lift all these high-mileage boats.
"Welcome to the party, guys," said Mr. Michel of VW. "Having a diesel in a Chevrolet will only promote the technology in this country."
This article originally appeared in The New York Times.