Engine technology has come a long way in just the past few decades. Perceptions have changed- well some of them- as people begin to branch out and try newer cars powered by new engines and the technology in them.

I remember just a few years ago trying to persuade a family friend that a 4-cylinder engine has changed- its no longer the boring, underpowered engine that it used to be. It can climb hills with ease- it is responsive, it's clean, it's small yet functional.

Other perceptions have taken longer to correct. The one I'm thinking of is the perception that diesel engines are slow, dirty, and only for trucks- which is wrong, wrong, and wrong.

For more on the diesel vs. gasoline debate, here's an article from Patricia Monahan and David Friedman of UCS.

If you or your parents owned a diesel car 20 years ago, you may have some bad memories of the experience. American drivers have steered clear of diesel since the early 1980s because many of the cars were unreliable, noisy, and polluting. Though today's diesel cars have overcome most of their past performance problems, they account for only a few percent of new automobile and truck sales in the US.

In Europe, on the other hand, about 40% of new cars sold are diesel, amounting to more than five million vehicles each year. The demand for diesel in Europe is fueled by the high cost of gasoline. (Unequal taxation of the two fuels results in diesel costing about one dollar less per gallon in most European countries.)

Over the past few years, diesel's popularity as an automotive fuel has grown significantly. Thanks to its higher energy content and its efficient combustion process, diesel performance enables cars to travel at least 30% farther on a gallon of fuel than comparable gasoline models.

The improved efficiency of diesel engines can also help reduce oil consumption. It should be noted, however, that it takes about 25% more oil to make a gallon of diesel fuel than a gallon of gasoline, so we should really look at how a vehicle does on fuel efficiency in terms of "oil equivalents." Thus, we need to adjust the mileage claims for diesel vehicles downward by about 20% when comparing them to gasoline-powered vehicles.

Americans continue to perceive diesel as a "dirty" fuel, though today that image is only partly deserved. Because of their lower per-mile fuel consumption, diesel engines generally release less carbon dioxide—the heat-tapping gas primarily responsible for global warming—from the tailpipe. So that's a check on the good side of the pollution chart. But when it comes to smog-forming pollutants and toxic particulate matter, also known as soot, today's diesels are still a lot dirtier than the average gasoline car.

All this means that diesel pollution can be deadly, causing premature mortality through cancer or heart and respiratory illnesses. The California Air Resources Board has concluded that diesel soot is responsible for 70% of the state's risk of cancer from airborne toxics. In the population as a whole, studies have shown a 26% increase in mortality in people living in soot-polluted cities.

To address diesel's emissions problems, tougher emissions rules are coming into effect. To meet the tougher pollution standards, high-tech diesel engines need low-sulfur diesel fuel. Unfortunately, US Department picture of refinery of Energy modeling has shown this fuel to be more oil- and carbon-intensive than reformulated gasoline.

Making a gallon of diesel fuel requires 25% more oil and emits 17% more heat-trapping greenhouse gases than gasoline reformulated with MTBE. Similarly, diesel requires 17% more oil and emits 18% more heat-trapping gases than gasoline reformulated with ethanol. This means that diesel fuel's advantages from its higher per-gallon energy content and better performance on greenhouse gases are partially offset by the impact of diesel's fuel-production process.

Still, future diesel vehicles, though perhaps not as cost-effective as gasoline, may have a role to play in reducing oil consumption and global warming pollution. Of the vehicles evaluated in the UCS report The Diesel Dilemma: Diesel's Role in the Race for Clean Cars, full hybrid-electric diesels offered the maximum improvement in fuel economy as well as the greatest reduction in heat-trapping emissions. But a key challenge remaining is whether diesel vehicles will ever be able to deliver the same progress on other air pollutants that we've seen in today's gasoline-power technologies.

Whether we're talking about diesel or gasoline, improved vehicle technologies have the potential to cut oil usage and global warming pollution by more than 50% while saving consumers money and protecting public health. It just takes the will to make it happen!