Diesel Debunked

By Alison Lakin
Ever take a deep breath, only to discover that the shaky, old diesel in front of you is filling your trailing car with a pungent odor? While those ancient oil burners won’t disappear anytime soon (they seem to last forever), the new diesels entering the market are radically less offensive to the senses. In fact, they are called “clean diesels" to signify their rebirth as a viable alternative to gas-powered cars. Automakers are hoping 2009’s diesel engines will change our perceptions of this fuel forever.

2009 Volkswagen Jetta TDI
2009 Volkswagen Jetta TDI

2009 BMW 335d
2009 BMW 335d

An essential reason the clean diesels sweep through stringent emissions standards introduced a few years ago (and avoid producing that awful smell) is the introduction of highly refined Ultra Low Sulfur Diesel (ULSD) to our fueling stations. Compared to old-school diesel, ULSD contains 97 percent less sulfur. The cleaner fuel became available in the U.S. during 2006 and is now found at almost every service station that carries diesel.

Jim McGill, Manager of Product and Technology Communications at Volkswagen, explains that Volkswagen “was reliant on ULSD to bring the clean diesels over to the U.S. and it is certainly a significant factor in emissions reduction."

With the introduction of ULSD, U.S. market diesel cars can make use of particulate filters and urea injection systems to reduce emissions to even lower levels than their gasoline powered stablemates. The systems can decrease the amount of particulate matter from the exhaust system by 90 percent. Most also use an additive in the catalytic converter to change normally harmful and polluting gases into harmless nitrogen and water.

“Aftertreatments like new particulate filters helped reduce emissions significantly. They took the sulfur ppm count from 500 to 15," continues McGill, “And a newer NOx storage system captured more emissions as opposed to letting them go out through the tailpipe."

Diesel engines also happen to be extremely fuel-efficient – something that hits close to home as the nation tries to cut down on its dependence on oil. Of course, diesel is still derived from the sticky black liquid, but choose the Jetta TDI instead of the regular Jetta and you’ll get 29 mpg in the city and 40 mpg on the highway compared to the standard 20 city and 29 highway. Using 30 percent less fuel equates to gas savings you can take straight to the bank and less reliance on oil overall.

Many clean diesel owners find that they get better gas mileage than the EPA estimates. Peter Vogel, who recently purchased a 2009 Volkswagen Jetta TDI, says, “I knew that the EPA fuel estimates were fairly conservative, but until I purchased the Jetta I never realized how badly they lowballed it. I've been finding 50 MPG or better on the highway."
A strong driving performance is yet one more beneficial characteristic of diesels. Their engines produce massive amounts of torque – no wonder it remains the fuel of choice for truckers. SUVs powered by diesel receive the same low-end twisty stuff as big rigs to help their hefty poundage get up to speed quicker. In cars with smaller engines, the torque makes for a zippy ride.

Additionally, automakers have long realized that diesels are best coupled with turbochargers. In layman’s terms, a turbocharger allows more air to be consumed by the engine. Since diesel engines ingest only air, the more air fed into the engine, the more power it produces. 

BMW, always aiming for number one, uses a twin-turbo system in their diesels. The first and smaller of the turbos cuts in during low speeds, while the larger one starts up when the engine's speed increases. The result of this is more power and more efficiency – two of our favorite things.

Since diesel engines as a whole are less complex than gasoline engines – they don’t have spark plugs or any type of ignition system - they need less maintenance. Their solid construction also tends to be more durable than gasoline engines in order to withstand the air compression pressure, making them last longer. This means less time at the auto shop and potential money savings in the long run.

Of course, diesel technology comes at a higher starting price than those fueled by gasoline, somewhat negating those savings. The Mercedes-Benz R320 BlueTEC, for example, starts at $50,025 while its gas-powered counterpart enters the market at $1,500 less.

But there’s a good reason for this mark-up, says McGill. “It’s more sophisticated technology. To meet the emissions requirements, you’re going to have more engineering time and more research and development."

There are eight other models tapped to come out in 2009. Audi, Mercedes-Benz, BMW and Volkswagen have produced diesels ranging from luxury SUVs to compact sedans. With a long history of diesel engine production, each of these German companies are primed to be front runners in the race to garner public support of clean diesel.

Much has been discussed about the future of the automotive industry and whether we’ll all be driving electric cars within 10 years or soaring about in hydrogen-powered flying saucers. Until alternative fuel technology becomes more advanced, our economy recovers and an infrastructure is developed to support the alternative fuels we are currently exploring, America needs a bridge to close the gap. Clean diesel technology is looking to be its keystone.

“There are many improvements that can be made to diesel fuel, and all indications are that today’s diesels will be able to run just as well on the fuel of the future, whether it be biodiesel or some other formulation," Vogel declares. “This technology is good for the long haul."

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