Absolutely, according to this article in Popular Mechanics. Would Americans buy such a car, if available? That’s an entirely separate question, according to the article.
BTW, Smart already sells a 60 mpg vehicle. That’s the desiel version, though. The gas version gets you only 40 mph. Here are stats on a few of the tiny cars now available, according to CNN.Money.
Smart ForTwo Mini Cooper Toyota Yaris
Base price <$15,000 $17,450 $10,950
MPG 40 31 37
Seats 2 4 4
Luggage space 5.3 cu. ft 5.3 cu. ft. 12.8 cu. ft.
Remember your basic thermodynamics: It takes energy to produce work, and there is a finite amount of energy in the combustion of gasoline and oxygen. Even in an ideal system, there is an upper limit to the number of mile-pounds (or kilowatt-hours, or btu's) that a gallon of fuel can produce. Figure in friction, conversion losses and other inevitable parasitic costs, and you can arrive at a more reasonable number.
From what I've read, the upper limit to unassisted mileage (no solar, wind, or gravity input) for a street legal sedan (4 seater) that meets the U.S. safety and emissions requirements, is about 60 mpg at highway speeds. I think you need a ceramic engine to get that, though. It burns hotter, more efficiently.
In my personal experience, on trips (such as Saint Louis to Banff to Vancouver to Denver and back) we average 40 mpg overall in our 1998 Mazda Protege sedan. On some tanks in the mountains get 50 mpg! At home, we only get about 33 mpg.
But if you limit your speed to 30 mph, and only accelerate once per tank, and only drive across a level plain, and don't use the A/C or electrical appliances (fan, wipers, lights, heater, etc), I'll bet you could get a reading near 100 mpg in any reasonably efficient car.
It's all a matter of where the energy is converted into work. A gallon of gas contains about 36.6 kilowatt-hours of energy. If you could completely convert the energy to electricity, it could run a room air-conditioner for about a day. In practice, you'd be lucky to get half of the energy in useful form, and the rest directly as waste heat.
Achieving higher gas mileage depends a lot on what you're willing to give up in trade. For example, a typical car requires only about a dozen horsepower to cruise at highway speeds, so virtually any car on the road could, in theory, do just fine with a small 4-cylinder engine. This is why some cars that are equipped with V-8 engines are designed to turn off one bank of cylinders when they reach highway cruising speed: those extra cylinders just aren't needed for the relatively light load of steady-speed cruising.
Unfortunately, of course, cars don't spend all their time cruising on the highway; they encounter other situations that demand higher peak horsepower. This is one reason why big vehicles don't have small engines: a 5000 pound SUV might be able to cruise down the highway with an 80 horsepower engine, but it will take a very long to accelerate to highway speed with such an engine. The SUV engine is designed to satisfy that peak power demand.
Hybrids use a different strategy. They use a small gasoline engine for "average" loads, then use stored battery power, instead of a larger gasoline engine, to deal with peak loads (e.g., acceleration). That's one why they perform as well as other cars, yet get significantly better gas mileage.
Not only does accelerating the car demand more power, but accelerating the engine does, too. Very high mileage could be achieved if all cars could be equipped with very small (e.g., 15 horsepower) engines that ran nearly all the time (at constant speed and at full throttle, which is relatively efficient), and then used stored energy (batteries, flywheels, fuel cells, etc.) for all power demands in excess of the minimum.
The weight of the vehicle also matters. When people who weigh 150 pounds are driving vehicles that weigh 3000-5000 pounds, the inefficiency is obvious.
Aerodynamics also matter. Beyond about 25-30 mph, most of the power needed for a vehicle are simply for the purpose of moving air out of the vehicle's path. Indeed, athletes on bicycles (who generate a maximum of about 0.2-0.3 horsepower) can easily top 100 miles per hour if they travel in the slipstream of a motor vehicle, where they experience negligible air resistance. Likewise, with an aerodynamic bodyshell, human-powered vehicles can easily exceed 40 mph on flat roads (the world record is well above 60 mph).
The bottom line is that 100 mpg in a consumer vehicle is almost certainly attainable, but the vehicle would need to be more lightweight, more aerodynamic, and have a more intelligent power system than vehicles currently on the market. Unfortunately, with the current cost (tax) structure in America, there is insufficient incentive for consumers to want such vehicles and, therefore, insufficient incentive for companies to invest in creating them.
The Indian car company Tata unveils a four-seat automobile that will sell for just $2,500. The Nano would be available later this year, and is aimed at people who might otherwise purchase a motorcycle. http://www.npr.org/templates/story/story.php?stor…
I'd bet that the Nano, like the Smart Car ( <a href="http://www.smartusa.com),” target=”_blank”>www.smartusa.com), will cost an additional $5,000 to bring it up to U.S. requirements. And all the additional mandatory equipment does cost in fuel efficiency.
But that's still a functioning car for well under ten grand and over 40 mpg.