Lifestyle

Squeezing Out the Extra Miles Per Gallon


There are plenty of futuristic fuel-saving technologies on the blackboard. What are automakers offering drivers today?

Like contestants on a reality TV show, automakers are being forced to reach an average of 35 mpg by 2020. That's a hike of more than 50% from today's levels and, after many pratfalls and a few tears, not everyone will be a winner.

Over the next 12 years carmakers around the world who want to sell their vehicles in the U.S. will be forced to spend billions overhauling existing facilities and developing new technologies to reach the federally mandated target set for the Corporate Average Fuel Economy standards. But in the meantime, before fuel cells and plug-in hybrids become more than just an ambitious idea, automakers are scraping for every possible mile per gallon to reach an average of 35 mpg.

To that end, the Detroit 3 and their import-brand rivals are greatly accelerating the spread of innovative, fuel-saving technologies that are less dramatically different but more affordable and readily available than gasoline-electric hybrids, battery-powered electric vehicles, or hydrogen-consuming fuel cells.

"Our emphasis is on the migration of advanced technology that is affordable and attainable in high volumes for all our customers," said John Viera, director of sustainable business strategies for Ford (F). "That 'high volume' part is important," he added, in an Aug. 11 press briefing in New York.

Every automaker, including Ford, is adding hybrid models. But hybrids have run into battery shortages. Meanwhile, the car companies are still trying to get all the bugs out of next-generation lithium-ion batteries, which are critical to the success of longer-range, plug-in hybrids and electric vehicles. And fuel cells are years, probably many years, away from mass production, and a hydrogen infrastructure that can support them.

Customer Benefits and Choices

The automakers can't wait, so they are turning to more readily available technologies. Under the hood, both domestics and imports are adding direct-injection gasoline engines that work on a principle similar to modern, clean-burning diesels. Whether gasoline or diesel, direct-injection engines spritz fuel directly into the engine's combustion chambers, at enormous pressure and at computer-controlled intervals. The result is cleaner, more efficient burning.

The customer benefit is more power and lower air-polluting emissions from the same size engine, with no mileage penalty, or else the ability to switch to a smaller engine that uses less fuel, without sacrificing power. For instance, the direct-injection gasoline version of the 3.6-liter V6 in the Cadillac CTS generates 41 extra horsepower at 304 hp, while achieving the same highway mpg as the standard engine, and only one fewer mpg in city driving, according to EPA estimates.

For the 2009 model year this fall, General Motors (GM) is adding the 3.6-liter V6 with direct injection as an option for its crossover vehicles, the Saturn Outlook, Chevy Traverse, GMC Acadia, and Buick Enclave. In addition, GM already offers direct injection for the Cadillac STS, the Saturn Sky, and the Pontiac Solstice.

Besides direct-injection gasoline, automakers—primarily the German manufacturers—are also reviving fuel-efficient diesel passenger cars in the U.S. The diesel-powered BMW (BMWG) 335d, for instance, gets 27% better highway mileage than the gasoline-powered 335i, with the same size engine.

No Loss in Power

Ford says it will offer so-called EcoBoost engines, combining direct-injection gasoline plus turbocharging, in 90% of its models by 2013. That starts next year with the Ford Flex crossover and the Lincoln MKS luxury car, plus the Ford F-150 pickup in 2010.

EcoBoost uses a combination of direct-injection gasoline technology with turbocharging, to produce a V6 with the power of a V8 but the gas mileage of V6. The same principle can also produce a four-cylinder engine with the power of a V6. The combined effect of direct-injection plus switching to a smaller engine with fewer cylinders is 10% to 20% better gas mileage, with no loss in power, Ford's Viera said.

Low-Rolling Resistance

Throughout their cars, automakers are also rolling out a host of less-visible but vitally important features that achieve better fuel efficiency by a few percentage points here, and a few percentage points there, like better automatic transmissions and low-rolling resistance tires.

According to Michelin North America, the physics of driving means an automobile has to overcome five forces: air or wind resistance; inertia, when accelerating, especially in stop-and-go city driving; gravity when driving uphill; internal friction, for instance, in the transmission; plus rolling resistance. Automakers are working on all those fronts.

Tires change shape as they roll, eating up some of the energy generated by the engine, and giving it off as heat. Low-rolling resistance tires fight that process with additional silica in the tread. Gene Peterson, tire program leader for Consumer Reports, said rolling resistance can vary as much as 50% from one type of tire to the next. That translates to as much as one or two miles to the gallon, taking into account other factors including inflation pressure, tire weight, tread life, and the road surface, he said.

Michelin estimates that also means low-rolling resistance tires can save about $400 to $600 in fuel costs in the life of a car, a spokeswoman said.

Slimming Down

Weight is another enemy of fuel efficiency. Ford's Viera said the company has a per-vehicle weight-loss target of 250 lb. to 750 lb. by 2020. For instance, the next-generation Ford Explorer will save weight by switching from a traditional truck platform to a more car-like unibody.

Ford's EcoBoost engines also represent a weight savings, since they replace a V8 with a V6, or a V6 with an in-line four-cylinder.

Besides smaller-displacement engines, all automakers are changing as much as possible within safety constraints to lighter-weight materials, like aluminum, magnesium, and plastics. Less weight also means the car companies can switch to smaller components within the car, like smaller brakes, since there's less mass.

"There is definitely a cascading effect," Viera said.

Click here to see the fuel-saving technologies that automakers are using now.

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