It's been said before, but this time it really does appear to be true: The diesels are coming. And this time there might be one that's just right for you.
Do you crave greater fuel economy, routinely drive long distances at highway speeds, hate visiting service stations, haul or tow heavy loads and enjoy quick acceleration?
If any of those define you and your needs, add diesel cars to your shopping list next time you are in the market for a car or truck. While it is true that diesels aren't for everyone, the advent of clean diesel fuel and advanced diesel engine and emissions technologies means there now are "oil burners" that mesh with an increasing variety of lifestyles and driving needs.
Audi, BMW, Mercedes-Benz and Volkswagen already offer a number of diesel models. And new diesels are here, or coming soon, from Audi, Chevrolet, Jeep, Mazda, Mercedes and Ram. With new launches in 2013 and as many as 10 new models coming for the 2014 model year, there soon will be at least 29 diesel passenger car, wagon and SUV models in the U.S. market.
Mercedes' GLK250 Bluetec 4Matic diesel SUV went on sale in late April and Chevrolet's Cruze TD (turbodiesel) hit the market in May.
The new 2014 Jeep Grand Cherokee diesel, the 2014 Mazda 6 Skyactiv-D diesel sedan and three new Audi diesels (the 2014 A6 TDI and 2014 A7 TDI sedans and the 2014 Q5 crossover SUV) are scheduled to launch later in 2013.
Finally, the Ram 1500 with a V6 diesel, the first modern diesel-powered light-duty pickup, also is scheduled to arrive later this year.
Diesel Advantages
Better fuel economy is the first advantage diesel backers usually cite to persuade passenger-car drivers with no previous exposure to diesels that they should start thinking about them.
It's a good place to start. Diesel engines use diesel fuel oil, which packs 14 percent more energy per gallon than gasoline does. And they put their fuel to use more efficiently than do most gasoline engines. In general, a diesel engine converts about 45 percent of its fuel to useful energy versus a gasoline engine's 30 percent efficiency. That means that a car or truck with a diesel engine typically offers 20-30 percent greater fuel economy than does that same vehicle equipped with a gasoline engine.
Diesels also offer more torque, which lets trucks do more work but in passenger vehicles often translates into snappier initial acceleration and a sportier driving experience than comparable gasoline models can provide. (We discuss torque in more detail later in this story.)
Diesel engines also are easier to turbocharge at high pressure than are gasoline engines. This boosts the automakers' ability to use turbocharging to downsize the engines and reduce costs while maintaining performance levels.
Because diesel engines use direct injection and compression combustion, which enables them to burn their fuel more efficiently, they also typically have lower lifetime maintenance costs than gasoline engines. There are no spark plugs or plug wires to replace and no high-voltage ignition systems to keep in tune. The engines themselves are built to withstand greater internal pressures from the powerful diesel fuel explosions in their combustion chambers.
It's true that some of the diesel advantage has been eroded by improvements in gasoline engines. Gas engines are getting better, thanks in part to some of the same technologies that have made diesels so efficient: direct injection and turbocharging, for example. But those gas engines are costlier, so the price differential with diesels gets smaller. And one advantage that diesels can continue to hold over gasoline engines is durability and longer engine life with fewer repairs. A diesel engine can last twice as long as a gasoline engine.
Diesel Disadvantages
On the downside, diesel fuel in the U.S. typically is more expensive than regular gasoline. And in recent years, it has been costlier in many regions than premium gasoline as well.
In part that's because the federal tax on diesel fuel is 32 percent more than the federal gasoline tax: 24.4 cents a gallon for diesel versus 18.4 cents for gasoline.
But diesel also comes from the same part of a barrel of crude oil as does home heating oil, so in the winter there's a lot of competition that keeps diesel fuel prices high. Because of federal low-sulfur rules, diesel fuel also requires expensive refining. The smaller demand in the U.S. for diesel vehicles also affects price. In Europe, almost half of all cars have diesel engines, versus a relative few here. As a result, U.S. refiners are net exporters of diesel fuel. European demand eliminates domestic surpluses that could help lower the price of the fuel in the United States.
Diesel fuel also isn't quite as available as gasoline. Only about half of all gas stations in the U.S., including highway truck stops and convenience store stations, have diesel pumps.
Finally, because diesel engines use such rugged parts and high-pressure fuel injectors, they are more expensive to build.
Pollution Solutions
When it comes to environmental concerns, diesel fuel is "dirtier" than gasoline. To meet federal requirements that tailpipe emissions be the same for both fuels, diesels need expensive soot traps and emissions filters and catalysts. Many diesel passenger vehicles require the periodic addition of a special urea-based diesel exhaust fluid when the oil is changed.
Although it helps swell the cost of a diesel car or SUV, all that added emissions treatment, along with the low-sulfur fuel required nationwide, means that today's diesels no longer spew smelly exhaust fumes and clouds of black smoke. Automakers still have to overcome many consumers' vision of diesel vehicles as smelly and dirty, though. It's a tough job, given that the image is continually reinforced by diesel buses and older heavy trucks that still ply the roads. But the truth is that emissions from modern diesel passenger vehicles are no worse than from today's gasoline vehicles.
Quieting Diesels Down
Another issue with older diesels is one that still colors many consumers' opinion: their (former) distinctive sound. In the past, diesel clatter woke sleeping babies, warned the neighbors you were coming down the street and in general let the world know that yes, a diesel had arrived.
That clatter was a combination of noise from the high-pressure fuel injectors and the echo from the highly explosive diesel combustion occurring in the cylinders. It was the audible signal that the engine was working.
But modern engine design and noise-reduction technologies have pretty much eliminated clatter as a problem. It is still audible from outside the cars when they are idling, especially in close and closed spaces such as alleys and garages. But if you're inside a modern diesel car or SUV, there's barely a hint of diesel clatter. And at speed, when the mechanical clacking is overpowered by wind, tires and general engine noises, it all but disappears.
Savings Versus Cost
A diesel version of a particular model typically will cost more to buy than a similarly equipped gasoline version. The range runs from a few hundred dollars to several thousand dollars and depends on real costs, plus each automaker's own pricing strategies. Mercedes-Benz, for example, charges almost no premium for most of its diesel models.
While diesels deliver better fuel efficiency than comparable gasoline models, they usually can't match the efficiency delivered by conventional hybrids. But in almost every case, the diesel premium is less than the premium that buyers pay for hybrids. Further, hybrids' fuel savings don't make up the difference. They remain more expensive to own than diesels.
Diesels' fuel savings can overcome the initial cost differences with gasoline models, but for some models it will take years of savings at the pump to do so. This story, Why Hybrids and Diesels Don't Always Save You Money, discusses the diesel-fuel payback period in more detail.
The Diesel Bonus
There also are savings that come with diesel ownership beyond the slow-to-accumulate fuel economy savings.
People who hang onto their cars and trucks for a long time likely will find that a diesel model will eat up far less time and money on repairs and downtime than will a long-term gasoline model.
Owners who pile on far more miles than the national average will see a quicker return on fuel savings and, likely, lower repair and maintenance bills than they might expect with a heavily used gasoline car or truck.
And when diesel vehicles are traded in, they historically fetch a substantial premium over gasoline models in the same condition and with comparable equipment. The resale "bonus" can often erase the initial purchase price premium that the diesel car carried.
Not Just for Truckers Anymore
In the past, diesel passenger vehicles in the U.S. have pretty much been limited to the pickup truck and full-size van markets, with Ford, General Motors and Chrysler's Ram division all offering heavy-duty models with big V8 diesel engines. They are offered to satisfy the needs of those who tow boats and trailers or haul hefty cargo loads.
That's because diesel engines have a much different operating profile than their gasoline counterparts, emphasizing torque, the mass-moving muscle of an engine, over horsepower. The short and very simplified explanation of torque vs. horsepower is that torque is the force that gets the vehicle moving and up to speed, while horsepower has to do with pushing the vehicle toward its top speed at high rpm as air resistance begins to loom large.
But now, drivers in the U.S. have begun demanding greater efficiency in the wake of increasing gas prices. And the government simultaneously is setting greater fuel efficiency standards to drive down both imported oil consumption and the greenhouse gas emissions that result from burning petroleum-based fuel. In response, automakers are beginning to fit more than just trucks with diesel engines.
Selection Growing
It's unlikely that diesel cars will ever get the market share in the U.S. that they have overseas. Consumer preference, fuel costs and government policy that aims to diminish use of all petroleum-based fuels will see to that.
But diesels account for less than 3 percent of all passenger vehicles registered in the U.S. today, and there's no reason that number shouldn't increase, says Allen Schaeffer, executive director of the Diesel Technology Forum, a national diesel industry advocacy group.
"In the last three years we have had the highest diesel [fuel] prices on record and the highest differential between diesel and gasoline on record," Schaeffer says. "We've also had a very tight economy."
Despite all that, consumers today are buying more diesel cars than ever before.
Granted, they started from a pretty small base, but diesel sales in the U.S. rose 25 percent in 2012 after a 27 percent increase in 2011. Schaeffer says he doesn't expect things to slow down very much.
"Consumer acceptance is growing, and with that and a national fuel economy mandate that will require a lot of very efficient vehicles, the number of diesel passenger vehicles could easily double in the next five years," Schaeffer says.
