After walking the aisles and meandering through the massive displays at the Detroit Auto Show, we've come to some conclusions. The green trend we've seen building has firmly taken root. Green is here to stay.

Manufacturers joining the green revolution are taking three general tracks. The first track uses known technologies and readily available fuels. The second taps alternative fuels such as ethanol with modified versions of existing internal combustion engines. The third looks further out in terms of time, this is where electric hybrids and fuel cell vehicles come into play.

Let's take a look at what we saw ...

Gasoline Engines Are Still Viable

With all the talk of hybrids and electric vehicles, one might believe that the gasoline engine is a dying breed. Nope. It just ain't so. Gasoline-fueled engines will continue to be improved for the foreseeable future.

Case in point: Ford Motor Company used the Detroit Auto Show to introduce its newest engine technology; Gasoline Turbocharged Direct Injection (GTDI). Engineering highlights of the technology include placing a single fuel injector directly in each cylinder's combustion chamber. This, when combined with turbocharging, helps dramatically improve efficiency. With GTDI, engine horsepower and fuel economy go up while emissions drop. It's a win-win solution.

Ford claims that GTDI enables vehicles that once required a six-cylinder engine to utilize a four-cylinder with no loss of performance. The same situation exists for SUVs and luxury cars that once may have required a V8. These could now find a GTDI V6 under their hoods.

At their press conference Ford also explained that the GTDI technology is much less expensive than diesel or hybrid power trains, so it provides fuel economy gains at a more affordable price than these other options. Expect to see GTDI four- and six-cylinder engines in Ford vehicles beginning this year.

Diesels Are Coming

Another fuel saving technology that manufacturers are turning to in the near-term is diesel. It may come as a surprise to some that diesel engines are among the oldest of engine technologies. Dr. Rudolph Diesel invented the compression-fired engine in the 1880s. Back then he ran his engines on diesel fuel refined from soybeans, what we call biodiesel today.

After years of powering giant trucks with names like Kenworth and Peterbilt, diesel engines will soon be much more common in US passenger cars and light trucks. (Diesels currently power about 60 percent of passenger cars in Western Europe.) Long shunned in the US because of their clattering noise and smelly exhaust, today's diesels equal the refinement of gasoline engines but provide superior fuel economy. Importantly, more efficient fuel combustion and emissions treatments have taken the stink and dirtiness out of diesel exhaust. There's no reason not to consider a diesel-powered car or truck save that there aren't many to choose from. That's about to change.

At the Detroit show, Dodge, Ford and Toyota all announced plans to offer new "clean" diesel engines in their light-duty (half-ton) pickups this year or soon thereafter. Today, diesel engines are only available in medium-duty models.

Also, at the press conference where Cadillac showed its handsome CTS Coupe Concept, one of this car's potential power trains was said to be the diesel V6 GM currently uses in Europe. While American drivers have never accepted diesel power in their luxury cars, that will change in the next few years.

Additionally, at the end of 2007 GM had already announced production of their all-new 4.5-liter Duramax diesel. This engine is slated to power the Chevrolet Silverado and GMC Sierra pickups. Because the engine is about the same size (externally) as a traditional small-block Chevy V8, it could also be used in a number of GM SUVs or passenger cars. The market should react favorably, as the engine produces great power (310 hp and 520 lb.ft. torque) with impressive fuel economy.

Mercedes' diesel news from Detroit came in the form of a new SUV that's about the size of a Honda Pilot or Toyota Highlander. The chiseled 2009 GLK bears a family resemblance to the larger Mercedes GL SUV, but instead of using a typical gas-guzzling V8, the GLK uses a diminutive but powerful diesel engine. The 2.2-liter four-cylinder is a fully modern clean diesel that meets tough new US emissions standards. The Mercedes GLK will take its place alongside the Mercedes E-Class BLUETEC diesel that is currently for sale in the US.

BMW also announced expanded availability of diesel power in their X5 SUV and their most popular car, the BMW 3-Series. Both will use a version of the company's sequentially turbocharged 3.0-liter in-line six-cylinder diesel. The engine uses two turbochargers, one tiny and one large. The smaller one spools up quickly to build power at low engine speeds, while the larger turbo takes over at higher rpm. The turbochargers help widen the engine's power band, making it feel similar to a high-performance gasoline engine while maintaining the kind of power that BMW owners demand (425 lb-ft torque) and improving fuel economy in both models.

To the joy of speed freaks everywhere, Audi placed a beautiful R8 center stage in their display. As if the R8 weren't pretty enough on its own, this version was the R8 TDI V12 Concept. It is powered by a 500-horsepower diesel engine that produces over 700 lb-ft of torque (staggering power). This model helps allay fears that a greener future is a more boring future.

Not to be left out, Honda hinted at their Detroit press conference that diesel engines are in company plans for US models. It's likely that the popular Pilot SUV could get the technology first. Subaru also announced that the company is studying the US market. In a manner typical of the conservative Subaru (and parent company, Fuji Heavy Industries) the company wants to see if consumers warm to diesel engines before they settle on an offering. Subaru offers diesel-powered vehicles in Asia and Europe.

Ethanol Is Emerging

In recent years, General Motors, Chrysler, and Ford Motor Company have produced millions of vehicles capable of running on E85 (85% ethanol and 15% gasoline). These vehicles have specially-equipped engines capable of burning ethanol and gasoline. Although the total number of E85-capable vehicles is impressive, there's one problem: the fuel isn't readily available across the country. Supporters of the fuel lament this fact because ethanol is renewable, helps engines produce more horsepower and burns cleaner than gasoline.

At one of GM's Detroit press conferences, Rick Wagoner came out in full support of E85, stating that as a country, the US needed to move a significant portion of its fleet toward ethanol. This came as a surprise to many, because there are genuine concerns about the present methods used to make ethanol. Currently, E85 requires a considerable amount of energy and water to produce.

Immediately after GM showed two E85-powered concepts, the Saab 9-4X and Hummer HX, their big news was the corporation's partnership with Coskata, a company that claims it can produce a gallon of ethanol for a dollar. The Coskata process uses 1/4 the water of current production methods, and can use many types of waste as the "feedstock" for the process. The company claims that it can use household garbage and even used tires to brew ethanol. With current methods of ethanol production driving up the cost of food products linked to corn (everything from tortillas to milk to beef), this new process could provide a valuable solution that will make ethanol-powered vehicles more viable in the coming years.

Joining the green bandwagon, Ferrari even feigned a degree of environmental friendliness with its ethanol-powered 430 Spider Concept. Using a modified version of the V8 found in the gasoline burning 430, because of E85's higher octane rating, the concept's engine is tuned to produce 2% more horsepower, for a total of 500. The corn-based fuel could make the iconic prancing horse gallop a little faster.

Hybrid Drive Systems

For the average driver, engines powered by gasoline and diesel will continue to improve in performance and efficiency. Ethanol may gain in popularity as ways to produce and distribute the fuel improve in the coming decades. Hybrid-drive systems and electric vehicles are further out in terms of mass sales, but their time is coming.

Many show stands in Detroit included at least one hybrid production or concept vehicle. A few had multiple versions of both.

In terms of sheer numbers, GM leads by a long shot. The company offers hybrid sedans (Chevrolet Malibu and Saturn Aura), a hybrid compact SUV (Saturn Vue Hybrid and Hybrid 2-Mode), and hybrid full-size SUVs (Chevrolet Tahoe, GMC Yukon, Cadillac Escalade). Plus, their expansive display in Detroit showcased their hybrid hit from 2007 (the Chevy Volt) and two newcomers, the Saturn Flextreme and Cadillac Provoq.

GM is still a couple model years from introducing a pure electrically-powered hybrid (today all high-volume hybrids combine an internal combustion engine with electric motors). Their 2008 concepts show the direction that GM is heading with its E-Flex hybrid platform. Each E-Flex based concept shares one thing in common; electric motors drive the vehicle. The concepts differ on how the vehicle's batteries are charged. The original Volt used a gasoline-powered generator, not completely unlike what you might fire up at the campground to provide electricity. The Flextreme uses a diesel-powered generator, an even more fuel-efficient choice. Both are certainly viable, as gasoline and diesel fuel are readily available. The Provoq uses a hydrogen-fueled fuel-cell to create electricity. This concept provides a picture of what's possible further out on the time line, as the infrastructure for hydrogen refueling stations is still decades away. If we were to place odds on what we'd see debut of the Volt sometime around 2010, we'd bet on something close to what's in the Saturn Flextreme.

Toyota, currently the manufacturer with the most popular hybrids (including its hot selling Prius), is continuing to expand its model offerings. Toyota offers a handful of hybrid models that carry Toyota and Lexus badges, but expect to see more, as the company has set ambitious sales goals. One of the most significant concepts shown in Detroit was Toyota's A-BAT. This awkwardly named truck features a Prius hybrid power train in a right-sized vehicle that could start an entire new trend toward smaller trucks. Because trucks have grown steadily over the past 20 years (today's compact trucks are the size of full-size trucks from 1980), there is room in the market for small, efficient trucks like the A-BAT.

Regarding hybrids, all manufacturers are struggling with battery technology. This single roadblock is holding back the GMs and Toyotas from bringing more electrically-powered hybrids to markets sooner. The breakthrough is coming, but it's still years away from production.

The Future Is Green

It's a trend that we've seen come and go a number of times in our 25 years in the auto show watching business. This time, we think the green trend is here to stay. As we cover more shows in 2008, we'll keep you posted as to what we learn. This is an exciting time to be watching the industry, as cars continue to improve in all areas of performance, including being green.

About the Author:

Rex Roy is a Detroit-based automotive journalist and author. He recently released a coffee table book, Motor City Dream Garages.

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