THE CURRENT 3% PENETRATION RATE for diesel engines in U.S. light vehicles might sound low, but diesel technology specialist Robert Bosch says that rate will more than triple to 10% by 2015.

Today, there are 20 light-vehicles nameplates available in the U.S. with modern clean-diesel engines, but that number will double in less than three years as auto makers position their portfolios to meet the federally mandated fleet average of 35.5 mpg (6.6 L/100 km) by 2016, says Peter Marks, chairman, president and CEO of Robert Bosch LLC.

Marks says many of the additional diesel vehicles will come from U.S. and Asian auto makers, which is significant because European marques have led the way with introduction of modern diesels.

“We are continuing to innovate and believe that diesel passenger cars of the future will run even more efficiently,” Marks says in a speech to the Automotive Press Assn. “So much so that a diesel-powered car in 2015 could exceed 54 mpg (4.3 L/100 km) of fuel.”

Less than two years ago, the future for diesel in the U.S. was in question as auto makers and suppliers such as Bosch feared the California Air Resources Board would legislate diesels right out of the market with next-generation LEV III emissions standards, which take effect in 2016.

Diesels emit higher levels of oxides of nitrogen and hydrocarbons, and early indications from CARB suggested extreme limits for such emissions were in the works and that the regulations heavily would favor electric vehicles.

Lars Ulrich, director-marketing for Bosch Diesel Systems in North America, says talks between CARB, the auto industry and the U.S. Environmental Protection Agency have been positive and the final decision from CARB regarding LEV III is due in November.

“We are optimistic that diesel will be enabled in 2016 and beyond,” Ulrich tells Ward's at the APA event. “That will further open the door for more diesel vehicles coming to market, certainly because now we have more clarity and predictability, which will drive further investments in this technology.”