Diesel, Gas or Hybrid?

The Auto Industry Is Pushing All Three, but Americans Aren't Sure


  • SUVs - Fuel Efficiency

    SUVs - Fuel Efficiency

    The Lexus RX 400h hybrid sport-utility, the Jeep Liberty diesel and the Toyota Highlander hybrid demonstrate the push by carmakers to find more fuel-efficiency for consumers.
    | March 18, 2010

The next time you're filling the tank and glare at the spinning numbers showing how much gas is costing, your mind might just slip away to visions of a perfect world.

In that perfect world, cars would be clean running and fuel would be cheap. And we're not talking about those battery-powered cars or hybrids that only get great mileage when you drive like an 80-year-old grandmother. After all, Americans like big engines and powerful acceleration, so the perfect car would have some get-up-and-go when you need it.

Now wake up because that perfect world of a clean, cheap and high-performance engine is almost here. In fact it is here, but you have to go to Europe to see it in action. It's diesel. And, for a couple of thousand dollars more, these engines get the same amount of horsepower with 30-percent better fuel economy and arguably lower emissions.

The European continent has fallen head over heels for diesel engines. In many areas, gasoline can run $5 to $6 per gallon, pushing consumers to look for other options. In fact, some 50 percent of new cars sold in Europe these days are diesels, up from 17 percent in 1992.

The only downside to vehicles with these engines is their price. They tend to be a couple thousand dollars more expensive than gasoline engines because they are more highly engineered, use more advanced technology and often require a turbocharger that kicks in to give added boost for acceleration.

The cost factor, combined with the relative affordability of gasoline in the U.S., has kept enthusiasm for diesels low. Furthermore, earlier forays into diesel technology in the 1980s were bungled by automakers leaving a sour aftereffect that lingers on.

Analysts have long predicted that diesels will make their move onto American soil when gasoline prices rise to prohibitive levels. And with the nation now shelling out more than $3 per gallon or more, the feeling is that time is now.

But a look at the makers of this engine technology suggests there is a bit of apprehension about what direction the North American market will head — and new breakthroughs in gasoline technology are giving rise to the notion that diesel might never win Americans away from their beloved gas engines.

How does diesel stack up against other conventional and alternative drivetrains? Here is a quick overview of the strengths and drawbacks of systems that are on the market:

  • Gasoline: Gas engines are relatively cheap and powerful. But they tend to be the least efficient type of engine and produce higher emissions.
  • Diesel: Diesel engines are powerful and efficient. Diesel fuel is easier and cheaper to refine from crude oil. But diesels are more costly by $1,000 or more because of the advanced technology to make these engines accelerate more quickly.
  • Gasoline hybrid: Hybrids like the Toyota Prius are on the road today. They get great gas mileage in the city by running partially on electricity. But they are more expensive than traditional engines by about 20 percent.
  • Diesel hybrid: Diesel hybrids are even cleaner and more efficient than gas hybrids. But they are also that much more expensive. This type of vehicle is still in development and may never fully come to market.
  • Ethanol/Flex-fuel: GM and Ford have been pushing this technology that allows cars to run mostly on ethanol — a corn-derived fuel that burns cleaner than pure gasoline. Many GM cars are already available with "flex-fuel" technology that run either gasoline or E85, a fuel that is blend of gasoline and 85 percent ethanol. On the up side, horsepower can increase when burning ethanol. On the downside, it burns faster as well, decreasing mileage. Even if you can find ethanol — there is currently very limited availability outside the Midwest — at this point it will end up costing you a lot more in the long haul.
  • Alternative fuels: These are cars that run on fuels like natural gas and hydrogen. For the time being, hydrogen cars are prohibitively expensive for normal passenger car use. Natural gas is affordable but fueling stations are scarce outside urban areas. A refueling device is now available that connects to a home natural gas line.

At the moment, gasoline, diesel and gasoline hybrid appear to be the major players for mass-market appeal. So the battle is revolving around them.

Gas hybrids have made a tremendous splash with big successes like the Toyota Prius and the Ford Escape hybrid. But many owners notice that when they get on the highway, the gains in fuel-efficiency are less impressive. And in the end, it takes a long time for the savings in gas to pay for the higher cost of a gas hybrid. As a result, while they remain popular, they aren't expected to dominate a major slice of the overall car market.

For a mass-market solution, the overwhelming popularity of diesel in Europe remains a top candidate. But a new hope for gasoline is emerging with the development of direct-injection engines that allow a gas engine to achieve lower emissions and higher horsepower depending on conditions.

Robert Bosch GmbH, an automotive supplier which makes diesel, gasoline and hybrid systems, recently demonstrated the direct-injection technology at its main test track in Boxberg, Germany. Bosch's system can be tuned to reduce emissions and increase efficiency by 15 percent in normal driving conditions. It can also retune itself to increase low-end horsepower for quick acceleration.

The system involves computerizing the fuel-injection process to spray gasoline in layers allowing it to burn more fully within the cylinder. The gas spray patterns can be altered depending on driving conditions to boost performance during acceleration or efficiency while cruising at constant speed.

The addition of a turbocharger further increases power while reducing consumption. This allows a smaller four-cylinder engine to produce the acceleration of a much larger engine, but still run efficiently when your speed is steady.

Basically, engineers are starting to add a high-tech element to gasoline engines helping them catch up to the superior performance of diesel. But it also comes with an increased price, which is, of course, the rub.

"Direct-injection engines resolve the conflict of objectives between driving dynamics and fuel consumption," said Rolf Leonhard, vice president of development for gasoline systems at Bosch. "Across the globe, gasoline direct injection with turbocharging will [help maintain] the current market dominance of the gasoline engine."

But within the same company, the diesel fans still hold faith their fuel will have as much success in America as it has in Europe.

And it seems to be happening already. Mercedes-Benz recently announced it would be pushing as many as four models of diesel-powered cars in the U.S. by 2008. And if gasoline prices continue to rise, the market for diesels could really heat up.

"Modern diesel engines are very attractive thanks to their high torque at low revs and their low fuel consumption," said Ulrich Dohle, president of diesel systems for Bosch.

And the debate ultimately will be decided by you.

The final answer to this riddle may be a blend of powertrains throughout the national fleet. Those around the industry are whispering that while gas may hold onto its dominance in the U.S. for cars, and hybrids will dominate commuting and city use, the truck market could very well switch over as the high torque output of larger diesel engines just doesn't match the high-tech gas engines.

"Turbodiesels especially make sense in the U.S. for SUVs and trucks. Who wouldn't want a midsize turbodiesel SUV with 310 horsepower, 553 pound-feet of torque and 23 mpg?" said Adriane Brown, CEO of Honeywell Transportation Systems, another supplier who is playing in this game.

The only definite is that because of stricter pollution requirements and a general need for consumers to use less fuel to save money, you'll likely be paying more for your engine's technology in coming years as the unrefined gas engine is slowly losing its standing in the marketplace.

Whether you'll be at the gas or diesel pump the next time you fill up, however, remains to be seen. But look forward to moving one step closer to that perfect world that motorists dream of.

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