The Little Engine That Could

Like Kermit the Frog, modern diesel engines are finding it’s not easy being green. But that could soon change.

As tough fuel economy standards go into effect — 37.5 mpg by 2016, and 54.5 mpg by 2025 — getting there won’t be easy. Fuel economy “has become the No. 1 concern of U.S. car buyers,” says Mark Fields, Ford Motor Co.’s president of the Americas. To meet the federal mandate, OEMs will offer a mix of solutions like slashing vehicle weight, improving aerodynamics, and migrating to more efficient power trains.

The Obama administration is offering several billion dollars in government-backed loans and grants to promote the development of tomorrow’s advanced engine technology, much of that to fund hybrids, plug-ins, and electric vehicles. But another alternative — the modern diesel engine — has gone largely ignored in the U.S., while in Europe diesels are favored by half of all buyers.

Today’s diesel engines aren’t the “oil burners” we Americans recall from the 1970s and 1980s. “There’s still the image of them being smelly, dirty, and slow, even though that’s not true anymore,” says Ed Kim, a researcher with AutoPacific Inc., a vehicle-forecasting firm with offices in Southfield. Modern diesels are quick, quiet, and clean — and phenomenally efficient. While Chevrolet hasn’t released numbers yet, a new diesel-powered version of its compact Cruze will likely deliver better highway mileage than the vaunted Toyota Prius, sources indicate.

The basic design of the diesel isn’t all that different from the gasoline engine. Both date back to the 19th century. Unlike a gasoline engine, a diesel uses extreme levels of compression, rather than a spark, to cause the air and fuel to self-ignite.

Where the best gasoline engines use perhaps a third of the energy stored in a given amount of fuel, modern diesels approach 50 percent. Credit for that goes to new technologies such as common rail fuel-injection and advanced turbo-charging.

To date, diesels haven’t caught on with American motorists (and green-minded politicians), but that could soon change. Chevy’s decision to offer a diesel engine in the Cruze “is a very strong statement,” says Allen Schaeffer, director of the Washington, D.C.-based Diesel Technology Forum. It sends the message that diesels are a mainstream solution.

While diesel offerings in passenger cars have been limited, some OEMs haven’t missed the steady rise in demand. For Volkswagen, BMW, Audi, and Mercedes-Benz, diesels account for as much as 30 percent of the sales on models where the engines are offered, such as on the VW Jetta.

As it stands, diesels this year will account for some 3 percent of the overall U.S. automotive market — more than all hybrids, plug-ins, and battery-electric vehicles combined.

AutoPacific projects that number will grow to 4.7 percent by 2016 — and that’s a conservative estimate, insists Diesel Technology Forum’s Schaeffer. “At the upper end we hear people talk about 15 percent in the 2015-16 time frame,” Schaeffer says. “We’re more realistically looking at 10 percent.” He wouldn’t have been nearly as optimistic a few years ago, but now can point to the Cruze and offerings from other OEMs as diverse as Mazda and Jeep.

There are still plenty of skeptics. Ford’s Fields points to the high cost of cleaning up diesel exhaust to meet ever-tighter emissions standards. “We think we can do just as well with our new EcoBoost technology,” he insists. Ironically, Ford’s new high-mileage gas engines make use of many of the advanced systems developed for modern clean diesels. But advocates say that as gasoline engine technologies continue to rise, diesels will become more competitive — even more so when compared to battery vehicles.

Where the diesel push runs into problems is at the pump. While availability is improving, diesel prices tend to run 20 cents or more per gallon higher than premium gasoline. That cuts into, but by no means eliminates, diesel’s overall cost advantage. When calculated over several years of driving 15,000 miles a year — the U.S. average — it still yields significant savings.

Another concern is the availability of diesel fuel. Prices are high, in part, because refineries have been straining to meet existing demand, never mind what might happen with millions of diesel cars running alongside those big 18-wheelers that clog our freeways. But many refineries are shifting to higher distillate output, as fuels like diesel and kerosene are known. Part of that is for export to markets like Europe. Still, a study commissioned by the Diesel Technology Forum last year suggests there’ll be more than enough fuel to avoid driving diesel costs any higher in the years ahead.

Industry planners like to say there’s “no silver bullet,” or no single solution, to the push for cleaner, more efficient automobiles. By decade’s end, most expect battery cars to become a serious part of the American automotive mix — but there are increasing signs that diesels will be a viable option no longer relegated to a quirky corner of the market. db