Does a Diesel Make Sense for Me?

With so much focus on improving gas mileage lately, hybrids have received much of the attention. But there's another technology that's worth considering: diesel power. While they're commonplace in Europe, in the U.S. diesel engines are mostly limited to heavy-duty trucks, buses and just a few consumer models. That's starting to change, though, as automakers are bringing new clean-diesel models to market. Let's take a look at some of the pros and cons of this technology. To see all available diesel vehicles, click here.

Diesels Offer Power and Efficiency

One of the main benefits of a diesel is improved efficiency compared to a similar-sized gasoline engine. Here, the Mercedes-Benz ML350 with its V-6 gas engine is compared to its sibling, the ML320 BlueTec, which features a diesel V-6.

Even though the two V-6 engines are fairly similar in size, and both SUVs use seven-speed automatic transmissions and have all-wheel drive, the fuel economy figures for each are significantly different. Based on the EPA's combined mpg rating, which is a proportional figure that factors in both city and highway driving, the diesel delivers about 20 percent better fuel economy, or about four extra miles per gallon of fuel burned. If you look at a passenger car like the Volkswagen Jetta, which is available with a four-cylinder diesel engine in the TDI model or an inline-five-cylinder gas engine in the SE, the fuel savings are even greater: The TDI offers 42 percent better combined fuel efficiency, or 10 more miles for every gallon of fuel burned.

Quiet and Clean

Modern diesel engines, such as the one available in the 2009 Volkswagen Jetta, exhibit less of the loud clatter old diesel engines were known for.

If diesel vehicles live in your memory as the loud and smoky machines of yore, it might be time to take a second look; modern clean-diesel vehicles have come a long way.

Cleaner ultra-low-sulfur diesel fuel and exhaust treatment systems on new diesel vehicles are designed to reduce emissions by 90 percent or more, according to the Environmental Protection Agency. You only have to stand near the tailpipe of one of these new diesels to see how different they are from models of the past; the exhaust they emit looks and smells no different than that from a gas-engine vehicle.

Modern diesels also exhibit less of the loud clatter older ones were known for. Sure, if you listen closely you'll be able to tell there's a diesel under the hood, but it's not as noticeable.

Diesel Downsides

So if diesels are so good, you might be wondering, why aren't they more widespread? For one, fuel efficiency only became so important to consumers recently, when the price of gas went up, so the better efficiency of diesels hasn't been a selling point that has resonated with shoppers until now.

Diesel engines also tend to be more expensive than comparable gas engines — sometimes thousands of dollars more expensive — as they often employ sophisticated technology like high-pressure fuel injection and a turbocharger.

Then there's the cost of diesel fuel. As of publication, the national average for a gallon of diesel was more than a gallon of regular gas, according to AAA. So even though diesel engines offer better fuel efficiency than gas ones, some of those savings are being wiped out by the more expensive fuel. However, with the way fuel prices have been bouncing up and down these days, the price of a gallon of diesel six months from now is anyone's guess.

Convenience is another factor that could keep some people from considering a diesel vehicle, as diesel fuel isn't as widely available as gasoline. But perhaps the biggest hurdle is whether or not automakers can change consumers' perceptions of diesels. If they can't get them to see past the dirty, loud diesels of the past, it's going to be tough to get them to give up their money for a clean-diesel car instead of a hybrid.