Diesels: Good, Bad, and Ugly

The price, for one. Never mind that diesel fuel consistently outranks premium gasoline as the most expensive fuel at the pumps these days—in some parts of California it still sells for over $3 per gallon, whereas gasoline prices are in the mid-to-high two-dollar range. Because of the scarcity of diesel-powered vehicles, most of the ones being offered in the U.S. wind up being pricey SUVs on the order of Volkswagen’s $60,000 V-10 Touareg diesel, or Mercedes-Benz’s $45,000 (and up) ML320 CDI and R320 CDI. (The situation may improve next year, when newer diesel engines hit our shores that are better-equipped to deal with more stringent North American pollution regulations.)

These two Mercedes we just mentioned don’t look any different than their gas-powered siblings (the ML series is more like a minivan-sized SUV, and the R series is a large-sized crossover-looking SUV). Mercedes-Benz has kept the price point of their diesel models to be about $1000 more than the gas-powered model, so you’re not paying a huge premium to get the oil-burner version.

Diesel fuel isn’t as difficult to source as you might think it is; 42% of U.S. service stations sell diesel. In fact, you can even go to Mercedes’ website and locate a station that sells it. If you’ve heard it said that diesel cars smell bad, relax: that’s only when refueling the car; you shouldn’t notice it when driving it. As for increased engine noise, the engine does sound gruff when it’s cold, but moderates the clatter when it gets warm. In fact, you’ll hear more engine noise outside the car than you will inside the cabin, thanks to Mercedes’ excellent soundproofing.

Don’t expect to race through an intersection from a standing stop—diesels (and especially turbocharged diesels, like this one) were never known for their get-up-and-go. However, if you’re already under way and you gun the accelerator, be prepared for warp factor 6—with 398 pounds-feet of torque at your disposal, you’ll easily be able to pass other vehicles while carrying lots of people and lots of cargo. Having a lot of torque at one’s disposal is one benefit of driving a diesel-powered vehicle.

As for that increased fuel efficiency? The Mercedes mentioned above get 21% to 33% better than their gas-powered siblings. As tested, they got mileage in the mid-to-high teens around town, and in the mid-20s on the highway. The R320 CDI racked up an impressive 550 miles on one tank of fuel going from Detroit to northern Virginia.
These cars run on the new ultra-low sulfur diesel fuel introduced last fall. About 80% of all service stations sell the new fuel, and almost all stations in urban areas do. If you don’t have the ultra-low sulfur fuel, you can still use the older kind of fuel that contains more sulfur, but the sulfur will gum  up the exhaust filters, which will need to be cleaned or replaced. Since that could be expensive, your best bet would be to only use the older type of fuel as a last resort.

So for only a thousand dollars more, you can get up to a third better mileage with Mercedes’ new diesel SUVs—if you’re willing to put up with some of the quirks of a diesel vehicle.

Via USA Today