DETROIT – Diesel engines offer about 20% better fuel economy over gasoline engines. But diesel fuel costs 20% more than gasoline in the U.S. It becomes a wash to many vehicle shoppers weighing the pros and cons of their purchase options.
So says Brian Bolton, Nissan’s senior manager-powertrain, at the Society of Automotive Engineers World Congress here during a panel discussion centered on diesel take rates for light vehicles.
Pump prices may play a big role in the future popularity of diesels in America, says Walter Riedl, a powertrain vice president for German luxury automaker BMW. “When gasoline is $2 a gallon, it’s tough for diesels.”
It’s less of an issue in Europe, where diesel popularity is much greater than in the U.S.
BMW is touting diesel versions of its 3-Series, 5-Series and X5 models, he says. “We’re trying to put diesels in the U.S. market, but it heavily depends on fuel prices.”
Panelists laud diesels for that superior fuel economy, as well as reliability, impressive low-end torque power and long-lasting durability.
They foresee increased market share for light vehicles powered by diesel engines in the U.S. but they also speak of hurdles to clear.
Among those is “intense competition from other powertrain technologies,” says Nissan’s Bolton. “There’s competition within the company.”
Powertrain engineers specializing in gasoline engines have made great technology advancements in recent times often by borrowing from diesel technology. “The gasoline guys are stealing from diesel technology,” Bolton quips. “Direct injection, which came from diesel, is now on 40% of gasoline engines.”
Also borrowed, or pilfered, from diesels are swirl-control valves, specific temperature-management systems and variable displacement oil pumps.
Gasoline and diesel powertrain engineers alike strive to improve their engines to meet government fuel economy and tailpipe emission regulations.
“New technologies create more costs, but the higher volumes of gasoline-powered vehicles on the market mitigate their costs,” Bolton says.
BMW’s Riedl says diesel-engine improvements in the works include emission reductions, increased pressure related to direct injection, optimized turbocharging, thermo-management refinements, use of lightweight materials and better-timed start/stop systems.
Annual diesel take rates have nudged up here and there in the U.S., but still lag far behind gasoline engines.
In 2010, sales of vehicles with diesel engines were 278,975 units, or 2.41% of the market, according to WardsAuto data. That compares with 10.99 million vehicles with gasoline engines, 95.2% of the market.
Last year, sales of diesel-powered vehicles were 445,621 units, 2.71% of the market. That’s more than five years ago, but a dip from 2.85% in 2013.
“There are some successful diesel segments in North America,” says Gary Arvan, chief engineer-diesel systems for General Motors. “Heavy-duty pickups are dominated by diesels.”
Vehicles with diesel engines are priced higher. For example, The MSRP for a diesel-powered Chevrolet Cruze is $26,485 compared with $22,195 for a Cruze with a gasoline engine.
“Diesels are almost always marketed as a premium option,” Arvan says. “Because of that, they must offer value to customers.”
Customer satisfaction is high among consumers who opt for diesels, he says. “Fuel economy is the No.1 reason they give for their purchase, and that remains a reason for their satisfaction during vehicle ownership.”
Lingering perceptions voiced by some diesel detractors are that the engines are noisy, smelly and hard to start.
Many diesel engines of the past were all of the above. But that’s not true of today’s diesels, Arvan says. “None of those things are mentioned by our diesel customers.”
A diesel fan is Roderick Renwick, Ford’s chief engineer-global engine engineering. He bought a diesel-powered heavy-duty pickup years ago, “and I’ve loved diesels ever since.” He notes diesels offer up to twice as much low-end torque as gasoline engines.
But increasing stringent government emission regulations will require extensive technology improvements, he says.
“Diesels will remain viable going forward,” Renwick says. "The challenge is managing the (technology) costs.”