A Guide to Diesel & Clean Diesel Cars

What Is A Diesel Vehicle?

1. List of Diesel Cars
2. Benefits & Drawbacks
3. Diesel-Hybrids
4. Biodiesel
5. Diesel Car News

A diesel vehicle uses an engine that has a different combustion cycle than a gasoline engine. In a gasoline engine, fuel is mixed with air, drawn into the cylinder, and ignited by a spark plug. In a diesel, air is drawn into the cylinder and compressed first without fuel present. This compression heats the air to such a high temperature that when fuel is then injected into the cylinder, it combusts.

By using higher compression ratios and higher combustion temperatures, diesels operate more efficiently. As a result, diesel vehicles attain better fuel economy than their gasoline counterparts. In addition, a gallon of diesel fuel contains about 10 percent more energy than a gallon of gasoline. These two factors help modern diesels achieve roughly 50 percent higher fuel economy than their gasoline counterparts. Diesel vehicles now account for nearly half of all new vehicle sales in Europe, and a small but growing market share in the US.

Illustration of Gas Engine compared to Diesel Engine

The List of Diesel Cars

Name	Combined MPG	Type	MSRP	Available	Description
Volkswagen Jetta TDI	35 MPG	Sedan	$21,900	Now	The Volkswagen Jetta TDI offers 140 horsepower, 40-mpg on the highway, and a wagon option.
Volkswagen Golf TDI	35 MPG	Sedan	$22,000	Now	Practical sporty clean diesel. Excels in highway MPG.
BMW 335d	29 MPG	Sedan	$44,700	Now	The 3-series with a 3.0-liter biturbo inline-six diesel powerplant.
Mercedes E320 Bluetec	27 MPG	Sedan	$52,300	Now	The E320 Bluetec luxury sedan uses a modern diesel system to deliver efficiency and eco-friendliness.
BMW X5 xDrive35d	23 MPG	SUV	$52,000	Now	High-performance, luxury SUV. Now more efficient as a diesel.
Jeep Grand Cherokee CRD	22 MPG	SUV	$34,400	Now	Following the success of the diesel version of the Jeep Liberty in 2005, Jeep now offers their newest diesel powertrain mated to the Grand Cherokee.
Mercedes ML 320 Bluetec	21 MPG	SUV	$48,600	Now	The most popular Mercedes SUV, available in fuel-efficient clean diesel version.
Volkswagen Touareg TDI	21 MPG	SUV	$42,800	Now	VW ditched V10. Now, the Touareg TDI comes reasonably priced and reasonably powered by a 3.0-liter V6 turbo diesel engine.
Mercedes R320 Bluetec	21 MPG	SUV	$49,100	Now	A big and heavy luxury station wagon with a clean diesel engine.
Audi Q7 TDI	21 MPG	SUV	$50,900	Now	Luxury seven-passenger clean diesel SUV with ultra-low emissions.
Mercedes GL320 Bluetec	20 MPG	SUV	$59,200	Now	The biggest, bluntest, and heaviest clean diesel SUV from Mercedes-Benz.
Audi A3 TDI	35 MPG	Sedan	$30,800	2010	A step up from the Jetta TDI Sportwagen, without going as far as expensive clean diesels from Mercedes and BMW.
Ford Reflex	n/a	Coupe	n/a	Concept	Concept sports coupe marries 1.4-liter turbo-diesel engine with Ford's hybrid drive.
Mercury Meta One	n/a	Van	n/a	Concept	A hybrid transmission with a twin-turbocharged V-6 diesel engine calibrated to run on biodiesel.

Diesel Benefits

Higher fuel economy
Diesel engines last longer, and fetch higher resale values
Diesel engines can be run on biofuel (biodiesel)
Diesels provide greater torque; great for rapid acceleration and towing
Driving range on a tank is longer

Diesel Drawbacks

Diesel fuel is more expensive in the US (In Europe, it’s taxed less heavily.)
Few models are available with a diesel engine
Particulate matter and NOx emissions are higher
Diesel vehicles are usually more expensive, although “clean diesel” carries purchase incentives
Diesel availability is more limited; there are fewer diesel pumps

Diesel-Hybrid Dreams

Toyota, Ford, Volkswagen, Peugot, and Citroën have all produced concept vehicles that mate a diesel engine to a hybrid system. The Citroën C-Métisse diesel-hybrid, unveiled at the 2006 Paris Auto Show, is pictured above. Combining the two fuel-saving technologies in one vehicle could produce phenomenal results. Volkswagen promises 70 miles to the gallon for a diesel-hybrid Golf expected to launch in Europe in 2009.

Unfortunately, the combined added expense of a diesel engine and a hybrid system are too costly. Most industry analysts predict that diesel-hybrids will be a niche product.

Biodiesel

Biodiesel is an alternative fuel used in diesel engines. Biodiesel, in its pure form, is not made from petroleum; instead, all or part of it is derived from plant oils or animal fats. In the United States, most commercial biodiesel is made from soybean oil, while in Europe, rapeseed (canola) oil is more commonly used. Biodiesel can be made from virgin oil, or from used cooking oil recycled from restaurants and food processing operations.

Biodiesel is a renewable fuel; to make more, we just grow more of the crop needed. It can be produced domestically, displacing imported petroleum. Biodiesel should not be confused with straight vegetable oil, which is untreated oil that some people use as fuel in their modified diesel cars. Biodiesel is a more standardized product that can be used in most diesel engines without any modifications. Like conventional diesel fuel, biodiesel can only be used in diesel engines; today’s hybrids with their spark-ignition, gasoline engines cannot burn biodiesel.

A walkthrough of the process of making biodiesel at home. It takes time to master the process, but with time and patience, you can produce your vehicle fuel right from home.

Unlike any other fuel for modern engines, biodiesel can be made at home without investing heavily in special equipment or earning a degree in chemistry. Many who make their own biodiesel use waste cooking oil as the base fuel, and restaurants are often happy to provide it to them free of charge. Other components for the reaction must be purchased, and time is required to master the production process. Once a user is experienced in making biodiesel, the per-gallon cost can be extremely low. Perhaps even more satisfying than the low cost is the knowledge that using biodiesel puts nothing in the coffers of major oil companies or major oil-producing nations and, in many cases, reuses oil that would otherwise be discarded.

Using pure biodiesel (B100) instead of conventional diesel significantly reduces emissions of hydrocarbons, carbon monoxide, and particulates, as well as output of carbon dioxide. Unfortuntately, EPA tests show that using B100 instead of conventional diesel results in 10 percent higher emissions of oxides of nitrogen, which can contribute to smog.

Top news inDiesel Cars

Carmakers Choose “Portfolio” or “Either/Or” Approach to Green Cars: The auto industry’s race for cars that use less petroleum and spew fewer emissions has multiple technology pathways. Major global automakers are now aligning into one of two camps. The “Either/Or” carmakers choose one technology and run with it, while the “Portfolio” guys market multiple technologies all at once.
Peugeot Diesel-Hybrids Get Real, Powered by Sanyo: The combination of a fuel-efficient diesel engine and a gas-electric drivetrain could push fuel-efficiency up and beyond 60 mpg. Volkswagen and Peugeot have shown concept diesel-hybrids for years, but have failed to commit because doubling up on the technologies means doubling up on the cost. But Peugeot is apparently breaking the ice.
VW Overwhelmed by Demand for Clean Diesel Sportwagen: Soaring demand for Volkswagen’s clean diesel Jetta Sportwagen TDI has left VW dealerships unable to keep up with demand. Waiting lists for the $24,000 vehicle—with MPG ratings of 30 city / 42 highway—are as long as 45 days in some Southern California dealerships. “We’re almost selling them off the trucks,” said Tom Wegehaupt, Volkswagen PR specialist, in an interview with HybridCars.com. “As soon as they’re on dealer lots, they’re gone.”
Audi Expects Big Gains for Diesels in US: Audi believes it can sell 20 to 25 percent of its vehicles in the United States with diesel powertrains. The company is pushing a political message—reducing foreign oil dependency by driving diesel—with ad and marketing dollars, but its executives aren't sure if it will pay off.
VW Unveils World’s Most Efficient Road-Legal Hybrid: By the end of the 2009 Frankfurt Auto Show, Volkswagen will have unveiled as many as nine world premier vehicles. What’s the common denominator? “Maximum efficiency," according to VW. The coolest in the bunch is the L1, a two-seat hybrid concept that could get hundreds of miles per gallon, and the E-Up! all-electric minicar. With these concepts, VW is pointing to small innovative platforms, new levels of aerodynamic design, and electric or hybrid drive.
BMW’s Green Sports Car Fantasy: “It’s the sports car of the future, the way BMW imagines it.” That’s how Adrian van Hooydonk, director of BMW’s group design, describes the “BMW Vision Efficient Dynamics” two-door concept vehicle to be unveiled at the upcoming Frankfurt Auto Show. Think of it as a showcase of the many fuel-efficient technologies that BMW has in various stages of development.
Frankfurt Auto Show Will Debut Diesels, Some Hybrids: Diesel is and will remain the solution for auto emissions in Europe. That’s the implied message based on the long and growing list of diesel debuts at next month’s Frankfurt Auto Show. Here’s our quick rundown of announcements so far.
BMW X1 Clean Diesel Bound for US?: BMW could bring a clean diesel version of the X1, its new compact crossover vehicle, to the US by 2011. “We’re hoping that by 2011, overall diesel sales will have ramped up in the US,” a source at BMW, who asked not to be named, told HybridCars.com. “If America starts to embrace diesel, it will allow us to market this vehicle with more confidence.” The clean diesel X1 would become the only vehicle in either the luxury class or the small SUV segment to offer more than 40 miles to the gallon in the United States.
Nonsensical Tax Credits Benefit Mercedes Diesel SUVs: One of the nation’s largest consumer incentives for energy-efficient cars—a tax credit of $1,800—goes to buyers of a $60,000-plus hulking diesel SUV that gets 17 mpg in the city. The Mercedes GL320 Bluetec and two other so-called “clean diesel” SUVs from Mercedes benefit from the tax credits. Meanwhile, today’s most efficient hybrids—such as the 50-mpg Toyota Prius and the 41-mpg Honda Insight, selling for $22,000 and $19,800 respectively—are not eligible for any federal tax incentives.
Kelley Blue Book Announces 2009 Top Green Cars: Kelley Blue Book, a leading consumer information website, announced its 2009 picks for the Top 10 Green Cars. Hybrid gas-electric cars top the list that also includes two small cars and two diesel engine vehicles. The number one choice is the 2010 Toyota Prius, a mid-size sedan offering a combined city/highway mileage of 50-mpg.