Driver's Seat: Is there a practical limit to fuel efficiency?

A shopper looks at the sticker of a Toyota Sienna in Raleigh, N.C. How does mileage compare vs. performance and "fun"?
A shopper looks at the sticker of a Toyota Sienna in Raleigh, N.C. How does mileage compare vs. performance and "fun"? (JIM R. BOUNDS / Bloomberg News)
Posted: July 13, 2011

So the government is going to mandate more stringent fuel-efficiency standards for passenger cars, perhaps as high as 56 m.p.g., come 2025, and automakers are worried about what it means for them.

My initial response? Tough luck for the automakers.

Every time there's a new government mandate, it seems automakers decry how impossible it would be to meet the standard and push for ways to reduce or lower it.

Seat belts. Catalytic converters. Air bags. Crash tests. They all met resistance from the folks who make the vehicles we drive.

But when I started doing some digging, I began to wonder if we've reached the point where engine technology, lightweight vehicles that still meet crash mandates, and consumer choice reach a critical point. Basically, maybe the manufacturers have a case regarding ever-rising miles per gallon.

More efficient engines?

I marvel at how vehicle horsepower has grown. Take, for example, my long-sold 1998 Pontiac Transport. The minivan produced 180 horsepower and burned a gallon of gasoline every 22 miles.

Today, I test-drive 2011 minivans with roughly 260 horsepower. They get 22 m.p.g. We could have traded that power boost for better fuel economy, right?

I asked Oliver Kuttner, founder and CEO of Edison2, a company at the forefront of design innovations for super-efficient vehicles. Edison2 created the Very Light Car and won the prestigious Automotive X Prize, and Kuttner would explain how simple this is.

But no. He said the industry cannot get very far with more efficient engines, especially when automakers are facing fuel-economy improvements of about 5 percent a year from 2017 to 2025.

"It is easy for the first year," Kuttner wrote in an e-mail from Kiev, Ukraine. "But every year it is harder. Imagine training your horse to eat less. At first it may be a good thing. But as you get it to be very good at eating less and less, one day it is dead."

Trading that 40 percent efficiency for a 40 percent increase in m.p.g. is not that easy.

Example: the 2011 Toyota Sienna. The van comes with two engine choices, a 2.7-liter four-cylinder that creates 187 horsepower and a 3.5-liter six that puts out 266. The EPA mileage ratings for the four are 18 m.p.g. city and 24 highway.

The six? 18 and 24.

Lighter weight

William Walton, manager of product planning for Honda cars, said lighter materials were a big part of the equation. But then cost quickly can become a factor.

The Acura brand, for instance, has used magnesium for oil pans, to save weight. But exotic materials will drive up the price for Honda buyers.

Kuttner sees design as the key. But getting materials that are light enough to save weight and strong enough to pass crash tests is a challenge.

Consumer choice

Walton and other auto-industry representatives agree that it comes down to what people want in their cars - and want to get out of their cars.

"We have more than 160 models of autos that get more than 30 miles per gallon," said Wade Newton, communication director for the Alliance of Automobile Manufacturers. "But they only comprise 4 percent of what consumers decided to purchase."

The power to run navigation and entertainment devices, air-conditioning, heated seats, and other comforts comes, of course, from the engine. Crash protection, antilock brakes, stability control, and computers to maintain everything in working order - they add weight to the vehicle, and reduce mileage.

Where to from here?

Doubling average fuel economy will not be easy. And it won't be cheap. But the time is now.

Hybrid technology, electric vehicles, alternative fuels, and diesels will play a big part in getting there. But consumers will have to turn their attention from moving as quickly as they can in the tallest vehicle they can find.

I have more fun driving a Mini Cooper (32 m.p.g.) or Ford Fiesta (35) than vans like the Chevy Traverse (17) or Toyota Sienna (22). Why would someone who doesn't require all those seats want the expense?

And I'm lobbying Mrs. Passenger to think outside the (minivan) box now that Sturgis Kid 2.0 will be joining 1.0 off at college.

Contact Scott Sturgisat 215-854-2558 or Read his blog at "A Different Spin" at Read recent columns at

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