By Mark Glover The Sacramento Bee

Published: Sunday, Jun. 9, 2013

Once derided as dirty and shunned by consumers, diesel cars have made a comeback in California as green machines.

While public attention has focused on flashier technologies like all-electric, hydrogen or hybrid vehicles, registrations for diesel cars and sport-utility vehicles jumped 55 percent in California from 2010 to 2012, according to figures compiled by auto information specialist R.L. Polk & Co.

The national growth rate in diesel cars and SUVs in the same period was a more modest 24.3 percent, said a recent Diesel Technology Forum report that contained the R.L. Polk information. In 2012, there were 84,106 diesel passenger cars and SUVs registered in California - 10.5 percent of the total.

California's strict standards for emissions and fuels eventually pushed dirty diesels to the sidelines, and by 1997, only Mercedes-Benz and Volkswagen offered diesel engine cars in the United States.

That very same year, however, the clean makeover of diesel began. Mercedes-Benz, proud of its diesel lineage dating back to the 1930s, introduced the Common Rail Direct Injection system, or CDI for short.

The complex system uses high-pressure fuel injection and computer-controlled electronic injectors to achieve more precise - and therefore cleaner - combustion.

Nine years later, at the 2006 North American International Auto Show in Detroit, Mercedes-Benz parent Daimler AG introduced its BlueTEC clean diesel technology for the Mercedes E-Class sedan.

The nucleus of the technology is AdBlue, an injected liquid solution that reduces smog-causing nitrogen oxide to nitrogen and water vapor.

BlueTEC's introduction dovetailed with the rollout of the ultralow-sulfur diesel fuel requirement in California, a standard capable of being met by diesel engines using green technologies that also included particulate filters.

Mercedes-Benz saw an opportunity. Ditto Volkswagen, which had remained doggedly committed to diesel.

At the 2005 Los Angeles Auto Show, Volkswagen AG Chairman Bernd Pischetsrieder told hundreds of journalists that diesels would remain VW's emphasis despite California's concern over emissions.

His remarks met with scorn from some California-based auto industry writers who insisted that hydrogen fuel and gas-electric hybrid technology were the future of environmentally friendly cars.

Three years later, at the 2008 Los Angeles Auto Show, the 2009 Volkswagen Jetta TDI was named Green Car of the Year. It got an estimated 41 miles per gallon on the highway and complied with emission standards in all 50 states.

The doorway for diesel was starting to swing open.

Today, the vehicle lineups of Mercedes-Benz and Volkswagen include multiple diesel passenger car and SUV offerings. And more competitors are trying to get a piece of the business.

Audi is making a big diesel push this year. Other diesel offerings are coming from BMW, Jeep, Mazda and Porsche.  Even Chevrolet - an icon among devotees of gas-fueled, internal-combustion engines - is heavily touting its 2014 Cruze "clean turbo diesel sedan," capable of 46 mpg.

While the per-gallon cost of standard diesel has been running ahead of the price of regular unleaded gas, diesel advocates are quick to point out that today's clean diesel engines are 20 percent to 40 percent more fuel-efficient than their gas-powered counterparts.

In the United States, diesels make up only about 3 percent of the passenger vehicle market, but the number of diesel models available in the U.S., now about 30, is expected to grow substantially in the next couple of years.

Not only that, an increasing number of diesel engines are capable of using diesel alternatives, including biodiesel.

Some local motorists driving diesel vehicles say they respect the proliferation of hybrid and electric vehicles in California, but they don't plan to switch anytime soon.

DIESEL VEHICLES IN CALIFORNIA

* California had a nation-leading 55 percent growth in registrations of diesel cars and sport-utility vehicles from 2010 to 2012. The state had 84,106 diesel cars and SUVs registered in 2012 alone, or 10.5 percent of the nation's total.

* When pickups and vans are included in the mix, California had 572,303 diesel vehicles on the road in 2012, 8.6 percent of the national total and trailing only 775,395 in Texas, a hotbed of pickup sales.

* Texas had a nation-leading 697,904 diesel pickup truck registrations in 2012; California was second with 461,035 (8.2 percent of the national total). By contrast, Texas had only 121,944 hybrid vehicle registrations last year, compared with 548,199 in California (nearly 24 percent of the U.S. total).

Source: Diesel Technology Forum, R.L. Polk & Co.