The Volkswagen diesel emissions scandal has taken a number of passenger-vehicle diesels temporarily off the market. But "circumstances involving a single manufacturer do not define an entire technology or an industry," asserted Allen Schaeffer, Executive Director of the Diesel Technology Forum (DTF), during a recent media event in New York. DTF is a trade organization including 12 OEMs from the automotive, commercial vehicle, and agriculture sectors, plus 13 suppliers and service specialists.
Despite VW's troubles that sharply reduced the available number of diesel passenger cars available in showrooms, there was a 4.2% nationwide increase in the number of diesel vehicles on U.S. roads in 2015, Schaeffer noted. Four states—California, Tennessee, Idaho and Nevada—had double-digit percentage increases, he said.
Favorable-unfavorable surveys show almost no change in the public's view of diesels since 2010 (47% positive for diesels, 27% negative). This appears to indicate the effects of VW's "dieselgate" were on the VW diesels' reputation, not the engine type itself or its fuel.
Schaeffer pointed to a specific survey in which only 12% said the VW crisis affected their perception of diesel fuel. A major factor is that most U.S.-market diesels are long associated with commercial trucks and vans, a segment in which the VW issue was barely a blip.
But the diesel engine does face challenges for light-duty vehicle applications, where OEMs need it to meet U.S. CAFE regulations, Schaeffer admitted. A major challenge is the higher cost of the engine, compared with gasoline units. This is not as much an issue in Europe where fuel subsidies and the diesel's premium reputation are offsets.
Fuel price comparison
The U.S.'s perpetual diesel fuel-price issue is complicated, in part because of low gasoline prices. During winter months, diesel fuel competes with home heating oil for the same fraction of the crude oil feedstock and thus is higher-priced. Most of the year, diesel transportation fuel is competitive with midgrade and premium gasoline and during the summer even with regular.
Further, as Schaeffer noted, buyers of diesel-powered luxury cars and SUVs are normally comparing the fuel price with that of premium gasoline, not regular. Diesel fuel's higher winter price is a smaller issue because drivers log fewer miles in winter, particularly with passenger vehicles.
The up-front extra cost (for passenger-vehicle diesels) is $2000 to $4000 in the U.S., based on engine size and manufacturer, it was pointed out by Alan Baum, a Detroit-based consultant who also spoke at the meeting. The option-price premium for light-truck diesels (2.8-3.0-L) is $4000 to $6000.
Baum said the increasing cost of content in gasoline engines could reduce the differential. However, Fiat Chrysler Automobiles, for one, has made it clear that although direct injection and turbocharging for its gasoline 3.6-L V6 are package-protected, cost is keeping those technologies on the shelf until needed for CAFE. The example proves OEMs are mindful of the potential costs for gasoline-engine upgrades.
Schaeffer told the meeting that the National Academy of Sciences technical assessment saw future improvements in diesel fuel economy. Efficiency upgrades could come from closed-loop combustion control and fuel-quality sensing from advanced fuel injectors or glowplugs with built-in pressure sensors, higher injection pressure (2500-3000 bar/37,000-45,000 psi) and cooled EGR. Also on the horizon could be integrating the SCR (selective catalyst reduction) function with the DPF (diesel particulate filter).
Although there presently is no satisfactory replacement for SCR with urea injection to meet the current Tier 3 emission standards, Schaeffer did project improvement from new catalytic coatings. Any upgrades, of course, would have to be highly cost-effective so they don't add to diesel's price disadvantage.
Managing cost for both diesel and gasoline engines will continue to be a balancing act, but diesel-fuel quality is another tradeoff factor. Although ultra-low-sulfur (15 ppm) fuel has been available since 2006, improvement is possible. Upgrades could reduce the amount of required SCR and other aftertreatment, boosting fuel economy.
The diesel impact on CAFE can be striking. For light-duty trucks, highway fuel economy numbers have reached 30 mpg (7.8 L/100 km) for FCA's Ram 1500, and 31 mpg for GM's midsize Chevrolet Colorado and GMC Canyon with the 2.8-L Duramax 4-cylinder diesel and 6-speed automatic. The Ford F-150's forthcoming V6 diesel, coupled with the GM-Ford 10-speed automatic, also is expected to exceed 30 mpg highway. Because the fuel economy requirements are based on vehicle footprint (wheelbase x average track), full-size trucks might be built to meet the 2025 CAFE standards with about 28 mpg (8.4 L/100 km) combined. This is based on CAFE two-cycle testing, which yields higher numbers than window-sticker procedures.
Engine designer and builder Cummins, which currently supplies Nissan with a 5.0-L turbodiesel V8 for the Titan heavy-duty pickup, has developed a 2.8-L diesel likely headed for Nissan's midsize Frontier pickup.
The EPA has a midterm review (for model years 2022-2025) that could relax CAFE, but as Schaeffer pointed out, "EPA recently was quoted as saying 'things are going well.'"
Diesel fuel availability
VW's self-inflicted troubles surfaced as virtually the remainder of the industry prepared to make major commitments to the diesel and with approximately 55% of gas stations offering at least one diesel-fuel pump, Schaeffer, said.
In addition to the F-150, he said, European OEMs will, for the most part, continue their dieselization product plans. Audi of America, however, recently announced it is cancelling plans for a 2.0-L diesel in its 2017 A4 sedan, citing greater demand for diesel in its SUVs.
The German brands have dominated the field because of Europe's regulatory structure. Cadillac is certain to join the diesel-vehicle roster to be competitive in Europe. And once VW diesels are recertified, Baum is certain diesel car sales in the U.S. will markedly uptick. A 1.6-L diesel is newly available for Chevrolet's Cruze and a 2.8-L Fiat diesel is coming for the Jeep Wrangler, to go with the 3.0-L V6 Jeep offers in the Grand Cherokee.
However, even if 100% bio-diesel were available and usable, Schaeffer said, a diesel cannot comply with California's zero-emissions mandate, so development of electric vehicles must continue.