By Warren Brown
Special to The Washington Post
Sunday, November 15, 2009
"Fuel efficiency" and "fuel economy" are relative terms. One speaks to the amount of work done per unit of fuel consumed. The other considers the amount and cost of fuel used per mile traveled.
To many of us, the terms are interchangeable. But meaning and truth are more nuanced.
Which is more fuel efficient?
Is it the tiny Smart Fortwo, which weighs 2,315 pounds and gets a combined city-highway mileage of 36 miles per gallon with a 1-liter, 3-cylinder 70-horsepower engine sipping required premium gasoline along the way?
Or, is it this week's subject automobile -- the 2010 Mercedes-Benz S400 Hybrid, a nearly 2 1/2 -ton luxury tank, replete with all of the comforts and conveniences of the modern, high-end car, that has seats for five people and a trunk big enough to carry all of their stuff, that gets a combined 22.5 miles per gallon with a gas-electric propulsion system yielding a maximum 295 horsepower, with the gasoline part of that system also requiring premium fuel?
Daimler, which makes both cars, argues that the big S400 Hybrid is in many ways as fuel efficient, if not more so than the little Smart Fortwo.
The S400 Hybrid weighs more, carries more people and stuff, and has considerably more oomph than the Smart Fortwo. In short, the S400 Hybrid does more work than the Smart Fortwo. Getting 22.5 miles per gallon, under the circumstance, is a pretty good deal.
The Smart Fortwo, which starts at $11,900 and gets 36 miles per gallon, is more economical than the S400 Hybrid, which starts at $87,950. But is the Smart Fortwo really more fuel efficient? It is less than half the weight of the S400 Hybrid, which weighs 4,815 pounds. It carries two people and very little of their stuff. It has substantially less horsepower. It requires the same grade of fuel as the S400 Hybrid. It is substantially less comfortable to drive. Yet, the Smart Fortwo beats the highway mileage of the S400 Hybrid by a relatively paltry 13.5 miles per gallon.
Which is more fuel efficient?
Had I the money, which is another variable affecting this discussion, I'd happily take the fluffed and tufted, automatic everything, fine wood-paneled, rich-by-design S400 Hybrid, a car that comes with class and environmental credentials. It is what the affluent world is coming to.
Hybrid technology and everything it means for fuel conservation and reduced tailpipe pollution has moved upscale to Lexus, Mercedes-Benz and Cadillac, among others. The filthy rich no longer need to restrict themselves to the likes of the humble Toyota Prius to prove that they are clean and green.
If you think that this is all about the environment, or all about reducing our dependence on foreign oil, you are mistaken.
It's mostly about image and marketing.
For decades, engineers at Daimler and other European car companies eschewed the development of gasoline-electric hybrids. The same was true for engineers at U.S. automobile manufacturers. They correctly pointed out that myriad other technologies -- advanced diesel engines; direct-injection, multi-valve gasoline engines; biologically derived fuels, liquid propane gas, compressed natural gas, lithium battery power, and hydrogen -- offered just as many advantages in fuel conservation and reduced air pollution.
But efficacious technologies such as hydrogen fuel cells were expensive and slow-developing. Alternative fuel technologies such as liquid propane and compressed natural gases lacked a certain sex appeal. In America, diesel erroneously remained equated with "dirty."
"Hybrid," by comparison, was quick, clean and clever -- at least in street presentation. Media leaders and politicians could wrap their minds around it. Some states, California and Virginia among them, went so far as to defeat the purpose of high-occupancy vehicle lanes to allow use off those corridors by hybrid vehicles with single occupants. But California and Virginia eventually recanted that silliness and reconstituted HOV lanes for their originally intended purpose, which is to reduce traffic congestion.
But, I stray. The S400 Hybrid is a beautiful car in terms of craftsmanship and overall performance. And it has bragging rights in that it's one of the first gasoline-electrics to use advanced lithium ion batteries instead of the heavier, less-efficient, nickel metal hydride and advanced lead-acid batteries commonly used in today's hybrid and all-electric cars. It's green for those with lots of green. Beyond that, I'd rather drive a diesel.
Wheego update: The 25-mile per hour, all-electric Wheego driven for this column Nov. 1 is of limited use and appeal. But the 35-mph Wheego driven subsequently makes much more sense and even borders on fun. Both versions are afflicted with dicey ride and handling that require acculturation for safe driving.