With an average national fuel cost currently hovering around three bucks for a gallon of regular, fuel economy matters. Over the past decade, the driveways of mainstream America filled with SUVs whose fuel-swilling was, at the time, not a concern. Fuel costs almost doubled from 1996 to 2006 and grew another 20 percent in the past year. The average U.S. household income, meanwhile, rose only 35.8 percent in the same 10-year period.

The associated shift in vehicle sales is telling. In 2007, sales of Chevy's Tahoe full-size SUV fell by 9.4 percent from 2006, while retail sales for the unlovable but frugal Chevrolet Aveo leaped by 82 percent. GM's John McDonald wrote this off as these vehicles' being "deferrable purchases," implying that land barges hold some kind of inherent allure and that Americans would prefer to drive dump trucks if gas were free. This is, of course, entirely possible.

But gas is not free, and we don't drive dump trucks, and as car buyers search for better fuel economy, they increasingly don't want to drive trucks of any kind. R&D dollars are focused on unibody crossovers that ad campaigns tout as more fuel efficient than the trucks they replace, with even Ford's Explorer headed for a frame-free future.

It's not just big trucks that get lousy fuel economy, either. The culprits of poor fuel economy are many, but common underlying causes include portly curb weights, older drivetrains, and the conscious exclusion of fuel-saving technologies to keep production and purchase prices down. Before you spend your money on a new car, make sure you pay attention to the equipment list, because with the wrong engine or transmission choice, heinous fuel economy is sometimes just a checkbox away.

2008 Saab 9-7X Aero

6.0-liter V-8, 4-speed auto, 4-wheel drive

12 mpg city/16 mpg highway

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Saab has expanded its ranks by making stepchildren of some decidedly un-Saabish vehicles. It started with the 9-2X, a.k.a. the Saabaru, a Subaru WRX wagon with a Saab schnoz and nice interior. Then came the 9-7X, a Chevy TrailBlazer with only slightly more-becoming clothes. As any Saab purist will tell you, it's not a real Aero unless you need Popeye forearms to do battle with the huge, turbocharged torque steer, absent here in spite of 395 pound-feet, thanks to the TrailBlazer's four-wheel drive.

The 9-7X Aero is fast, however, as you'd expect of nearly anything with a 390-hp Chevrolet LS2 V-8 under the hood. If you need more evidence that the 9-7X is as Swedish as General Tso's chicken, it comes with 20-inch polished wheels. Ostentation is to Swedish culture what showmanship is to the NFL's Manning family.

The 9-7X is the first Saab ever not to feature unibody construction, instead relying on body-on-frame technology proven road- and trailworthy by the Donner Party. Although lesser 9-7Xs already manage only questionable fuel economy -- the thriftiest engine is rated at 14/20 mpg -- let yourself be talked into the top-of-the-line 9-7X, and you'll be looking at quite a bottom line at the gas pump. The Chevy LS-series V-8s can be relatively frugal when properly geared, but with a four-speed automatic, all-wheel drive, and 4800 pounds to lug, this 6.0-liter returns a bottom-of-the-list 12 mpg in the city and 16 on the highway.

2008 Jeep Wrangler

3.8-liter V-6, 4-speed auto, 4-wheel drive

15 mpg city/19 mpg highway

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That Chrysler's most rugged product, the Wrangler, is capable of transporting you farther into the wilderness than almost any other production vehicle while doing a knock-up job of spoiling it is a head shaker.

We understand that a Wrangler is heavy by virtue of super-extra-beefy parts and a frame that could double as a railroad truss, that a rock crawler's engine needs to be dead reliable and much proven, and that this true mudslinger needs to be held to a low price point, but c'mon. We realize it's cheaper to use really thick steel than forge stuff, but if the compact Wrangler didn't weigh two tons, it might get better gas mileage than the much-larger six-cylinder Grand Cherokee.

Jeep's "modernization" of the Wrangler's powertrain for '07 meant replacing the venerable 4.0-liter straight-six, not much evolved from what you got with an AMC Rambler American in 1965, with the 3.8-liter pushrod V-6 designed to have its oil-change intervals neglected by 1991 Chrysler Imperial owners. Mileage is stuck at 15 city/19 highway regardless of transmission choice.

No one expects a Wrangler to be anything but torquey, something easily accomplished with things such as engine stroke and proper gearing but also quite well handled by diesels. As a known spray-tan solvent, that fuel might compromise the lucrative fraternity market, but we'd love to see Jeep drop in a Mercedes diesel or wait for DDC Cento, which supplied the unit in the now-extinct Liberty CRD, to clean up its act.

2008 Jeep Liberty

3.7-liter V-6, 4-speed auto, 4-wheel drive

15 mpg city/21 mpg highway

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Jeep makes it known its Liberty is indeed a Jeep by offering two all-wheel drive systems, the part-time Command-Trac and full-time Selec-Trac II. It's too bad the only available engine is a stinker, and not because it's a diesel; the previously available diesel didn't meet 2007 emissions standards.

The 3.7-liter PowerTech V-6 follows in a grand Chrysler tradition of dubiously optimistic names like Caravan Sport. Plenty of equally sized engines make more power -- Nissan's 3.7-liter VQ37 makes 120 more horsepower -- and although it does have overhead cams, that's about where the tech ends.

The only Jeep worth having is one with four-wheel drive, and most customers choose an automatic. So equipped, the Liberty returns fuel economy of 15 mpg in the city, 21 on the highway. The Liberty's mechanical (and arguably aesthetic) twin, the Dodge Nitro, is offered with a 4.0-liter V-6 producing an additional 50 horsepower and 30 pound-feet of torque, with just a 1 mpg highway penalty.

Much like the Wrangler, the Liberty's salvation lies in the return of a diesel or doing something about the more than two-ton curb weight. Chrysler might, however, have it right: People would rather line the pockets of the oil barons every time they fuel up rather than pay more money up front for a more-fuel-efficient vehicle.

Next Page: Saturn Vue XE, Pontiac G6 GT Convertible, Mazda RX-8 & Mazda CX-7

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