Video: Putting cars on a diet

Image: Paul A. Eisenstein, contributor
By contributor
updated 5/5/2011 8:17:30 AM ET 2011-05-05T12:17:30

With gas prices pushing past the $4-per-gallon mark, fuel economy has become a big issue for car buyers and carmakers alike. Yet many U.S. motorists still seem reluctant to embrace the sort of pint-sized vehicles that have become commonplace in markets like Europe and Japan.

“People don’t necessarily want to drive small cars,” stressed George Peterson, an automotive analyst with AutoPacific. “They want to drive bigger, more fuel-efficient cars.”

Given American car drivers’ tastes, some experts suggest that the challenge for automakers today isn’t to come up with a subcompact car that does 50 mile to the gallon. Instead, the challenge is to build a midsize model that can deliver 40 mpg.

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Until recently, achieving that goal seemed like a fantasy, at least without using a costly hybrid drivetrain. But carmakers have come to discover a variety of other tools in their toolbox that can improve mileage substantially without downsizing, Peterson said.

At Ford, for example, they’re putting vehicles on a diet.

“In the mid-term, from now to 2017 or 2018, we’ll remove anywhere from 250 to 700 pounds, depending on the vehicle,” said Derrick Kuzak, Ford’s global product chief.

According to an industry rule of thumb, every 100 pounds added or subtracted from the mass of a vehicle has a one mpg impact on fuel economy, so Ford’s weight reduction strategy should yield anywhere from around two to seven miles a gallon in added fuel economy, everything else being equal.

Ford is by no means the only maker targeting heft. Hyundai pulled about 150 pounds off the curb weight of its new Accent subcompact, which helped it achieve a highway rating of more than 40 mpg.

And Honda is taking similar steps. John Mendel, chief executive of the automaker’s U.S. subsidiary, has said, referring to improving fuel economy, that “there are only so many levers you can pull, and two of the biggest are weight or size.”

As anyone who’s ever tried to shed a few pounds for a wedding or a reunion knows, dieting isn’t easy. And it’s especially tough for automotive engineers. Every year seems to bring new safety regulations demanding new equipment for cars, like stability control, or stiffer bodies that can survive the latest roof crush standards.

Add all the onboard features that consumers are demanding, from heated and cooled leather seats to twin headrest-mounted backseat video monitors, and the challenge of slimming down becomes even harder.

“Which is why, despite all our efforts in the industry to cut weight over the last decade, the weight of most vehicles have actually gone up,” lamented Carlos Tavares, president and CEO of Nissan Americas.

Worried about losing business, steel makers have been coming up with a variety of super-strong alloys that actually reduce the amount of metal needed in a car, even with the tougher roof crush standards.

But the industry is also migrating, where possible, to newer, lighter alternatives. The latest Jaguar XJ, for example, uses an aluminum body and chassis, while the new Porsche 911 GT3 RS 4.0 has super-light carpets.

The Porsche Cayenne redesign has shed a full 408 lbs with the use of lighter materials and a revised drivetrain. Across the line it gets at least a 10 percent mileage increase, yet with the twin turbo V8 model the car’s 0-60 acceleration time drops from 4.9 to 4.4 seconds.

Aluminum can shave hundreds of pounds off the weight of a conventional steel car body. And the metal is in steadily increasing demand, as is magnesium, which is used for such applications as the cross-beams mounted behind many modern instrument panels.

Plastic, in all its many forms, has become the material of choice for bumper fascias, interior trims and even some body panels — although the now-abandoned Saturn brand gave up on using the material for fenders and doors because of a nasty tendency to shrink and swell, depending on the outdoor temperature.

The material of the future, many are betting, is carbon fiber. Seemingly as light as air, the material has become extreme popular with manufacturers of high-priced sports cars, like Lamborghini, which uses carbon fiber for much of the new 200 mph Aventador sports car.

The problem is cost. Using carbon fiber in a car has traditionally required a price tag in the $200,000 range, but that may be changing. At the Geneva Motor Show earlier this year Mini showed off the Rocketman concept, which would use carbon fiber on a car priced at barely a fifth as much as Lamborghini’s Aventador. Mini’s parent, BMW, has invested in carbon fiber research, as have a number of other makers.

“Carbon fiber has potential if we can come up with ways to improve manufacturability and bring down costs,” said Ford’s Kuzak.

The Detroit automaker’s engineering czar stressed that it’s difficult to put an existing vehicle on a diet. Instead, it’s better to start with an all-new car platform. One of the advantages with this approach is that if you cut a few hundred pounds from a vehicle’s overall weight you can save even more by then adopting a smaller engine, downsizing the brakes and other components.

While Ford has been pushing to trim mass even faster than before, Nissan’s Tavares cautioned that “you should not only focus on weight reduction.”

There are plenty of other ways to impact fuel economy, including aerodynamics, improved tires and reduced-friction powertrains, he said. By investing in all these areas, automakers still have plenty of opportunities to improve mileage enough to let buyers downsize their fuel consumption without having to give up the larger cars they like.

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Explainer: Ten cars with surprising gas mileage

  • Image: 2011 Chevrolet Corvette Coupe
    GM  /  Wieck
    The 2011 Chevrolet Corvette Coupe delivers an impressive 26 mpg on the highway.

    Everyone and his goldfish knows that you can get good gas mileage by driving a Toyota Prius. But many of us want to buy cars with features that typical high-mileage economy cars don’t provide.

    Those requirements don’t have to doom us to terrible fuel economy; we just have to choose our cars more carefully. So here’s a list of 10 vehicles with unexpectedly good fuel economy for their size and/or vehicle type.

    (Note: This is not a list of the 10 vehicles with the best fuel economy; you can find that list on the EPA’s website).

  • Audi Q7 TDI


    EPA MPG city/highway/combined: 17/25/20
    Drivetrain: 3.0-l V6 diesel, 8-sp man.
    Vehicle category: 7-seat SUV

    With the Q7 you really can average 25 mpg on a long trip in a sure-footed quattro all-wheel-drive, three-row, seven-seat SUV. You do have to fuel it with diesel, which costs a bit more than gasoline, but you will only have to do that every 600-something miles. And you won’t pay any other penalties because the performance and smoothness of the drivetrain are indistinguishable from that of a comparable gas turbo V6.

  • Buick LaCrosse eAssist

    GM  /  Wieck

    EPA MPG city/highway/combined (estimated): 25/37/31
    Drivetrain: 2.4-l 4-cyl. Hybrid, 6-sp auto
    Vehicle category: mid-size car

    Here’s a midsized Buick — with all the luxury the brand implies — that delivers 37 mpg on the highway. The old advertising slogan was “Wouldn’t you really rather drive a Buick?” The answer to that question for many

    years was “no,” but now that the company’s products have become excellent, if the alternative is some cramped, buzzy econobox, here’s your 37 mpg solution. Because of the compact size of the “eAssist” mild hybrid system, the rear seats fold flat for a pass-through from the trunk — a feature that isn’t available in full hybrid sedans because the space behind the seat is occupied by electric drive electronics.

  • Chevrolet Equinox

    GM  /  Wieck

    EPA MPG city/highway/combined: 22/32/26
    Drivetrain: 2.4-l 4-cyl, 6-sp auto
    Vehicle category: SUV

    Compact SUVs are the new family cars for many consumers, but even though they aren’t gargantuan ground-pounders, they can still get pretty mediocre fuel economy, especially when equipped with a V6. Chevy has dropped in a brawny-but-smooth four-cylinder that delivers 32 mpg in highway driving, and buyers have been snapping them up as fast as the company can build them.

  • Chevrolet Corvette

    GM  /  Wieck

    EPA MPG city/highway/combined: 16/26/19
    Drivetrain: 6.2-l V8, 6-sp man.
    Vehicle category: two-seater

    No one buys sports cars for their fuel economy, but wouldn’t it be nice if some ludicrously fast 430 hp rocket also delivered 26 mpg on the highway? Well, here it is. The Corvette will crank out mile after mile of mid-20s mileage while you’re on the highway driving to the best curvy mountain roads or some distant race circuit for a bit of track day fun.

  • Ford Fusion Hybrid

    Ford  /  Wieck

    EPA MPG city/highway/combined: 41/36/39
    Drivetrain: 2.5-l 4-cyl. hybrid, CVT
    Vehicle category: midsize car

    Here’s the most efficient vehicle on this list, with 39 mpg in combined driving — the 41 mpg city, 36 mpg highway Ford Fusion Hybrid. It doesn’t carry the humpbacked styling or overt political connotations of a Prius, but it does deliver nearly the same gas mileage in a vehicle with a more comfortable ride and vastly better handling.

  • Ford F-150

    Ford  /  Wieck

    EPA MPG city/highway/combined: 17/23/20
    Drivetrain: 3.7-l V6, 6-sp auto
    Vehicle category: full-size truck

    It takes energy to move a load, and that energy comes from gas. Trucks burn more gas than cars even when they aren’t hauling loads because they are built big and sturdy enough to withstand heavy-duty use. That has typically meant that gas mileage ranged between “dismal” and merely “bad.” But Ford’s new V6-powered F-150 has achieved the widely accepted threshold of “decent” gas mileage — 20 mpg. That’s the truck’s combined EPA rating, and they EPA says it can do even better on the highway at 23 mpg. Our testing scored 20 mpg highway too, but other reviewers did better. Regardless, it is a big step forward considering that old trucks wouldn’t go 20 miles on a gallon of gas even if they started driving atop the Continental Divide.

  • Honda Odyssey

    Honda  /  Wieck

    EPA MPG city/highway/combined: 19/28/22
    Drivetrain: 3.5-l V6, 6-sp auto
    Vehicle category: minivan

    Remind me: Why do we call these things “minivans” again? They were pretty small when they started out, but now they are 4,500-pound, eight-passenger behemoths. It would be asking a lot for something this big to get reasonable gas mileage, but the Odyssey delivers, using cylinder deactivation to run on three cylinders when possible, along with a six-speed transmission to get the power to the wheels as efficiently as possible.

  • Hyundai Sonata

    David McNew  /  Getty Images

    EPA MPG city/highway/combined: 24/35/28
    Drivetrain: 2.4-l, 6-sp man.
    Vehicle category: large car

    The Hyundai Sonata has a smidge more interior space than the Fusion or LaCrosse and rates 35 mpg highway with its base engine and transmission. Hyundai also offers a hybrid version, but the everyday model provides 35 mpg on the window sticker, and anecdotal evidence says it will even get 40 mpg on the highway.

  • Hyundai Elantra


    EPA MPG city/highway/combined: 29/40/33
    Drivetrain: 1.8-l 4-cyl, 6-sp auto
    Vehicle category: Compact car

    Forty mpg might be a stretch for the Sonata, but the compact Elantra should do that without breaking a sweat, according to the EPA’s 40 mpg highway rating. As with the bigger Hyundai, the Elantra achieves its segment-benchmark fuel economy rating with its base drivetrain, so the hundreds of thousands of Elantras the company sells will all contribute to the fleet of 40 mpg cars on the road. This is in contrast to the special, high-efficiency models from competitors, which cost more and will account for a paltry few percent of sales.

  • Volkswagen Passat


    EPA MPG city/highway/combined (estimated): 31/43/35
    Drivetrain: 2.0-l 4-cyl. diesel, 6-sp. dual-clutch auto-manual
    Vehicle category: large car

    If the diesel engine in the Q7 can get 26 mpg on the highway, what could one in a slippery sedan achieve? According to VW, the answer will be 43 mpg when the EPA’s official numbers are announced. That means the Passat will go more than 800 miles on a tank. Those of us who love pumping gas in the freezing cold or blazing heat might miss standing out in the weather regularly, but for the rest of us, incredible efficiency matched with a large fuel tank combine to provide unprecedented freedom from pumping fuel.


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