Can a car get 100 miles per gallon?

In addition to the Toyota Prius, has worked on the Ford Escape Hybrid to allow it to plug into a standard electrical socket. See more pictures of hybrid cars.
Image courtesy Consumer Guide Automotive

The average American car today gets about 20 miles per gallon (mpg) of gasoline. Eighty years ago, Henry Ford's Model T got 25 to 30 mpg and that car could run on gas or ethanol. What happened? In the decades since the Model T, car technology, speed, safety and comfort have improved tremendously. But in terms of fuel economy, we're still decades behind. With concerns about gas prices, global warming and air pollution, fuel efficiency has already become a point of concern for car buyers. Let's explore the question that a lot of people are asking: Can a car get 100 miles on a single gallon of gas?

We're not the only ones asking the question. Google -- yes, the search engine Google -- is trying to find out.



On June 20, 2007, Google announced that its founders' philanthropic organization,, is modifying gas-electric hybrid vehicles like the Toyota Prius to try to breach the 100 mpg threshold. The project, called Recharge IT, is collaborating with other companies and researchers, including Pacific Gas & Electric. They've handed out $1 million in grants to think tanks, educators, advocacy groups and researchers to advance the hybrid cause. Another $10 million is available to researchers who offer worthy proposals.

RechargeIT features a standard Prius that's been modified to connect to a 120-volt electrical outlet. Two of these vehicles are being tested against two standard Prius hybrids. Together the two plug-in Prius hybrids are averaging 73.6 mpg, while the standard Prius hybrids are ticking along at 40.9 mpg [Source: Google]. The plug-in hybrids have also shown a significant decrease in CO2 emissions.

A second, intriguing part of the Google project is that they're working on vehicle-to-grid (V2G) technology, which lets cars "sell" back excess stored-up electricity to the local utility's electric grid. The vision behind this technology is discovering ways to harvest energy that's produced when driving a car -- engine heat, friction from breaks, solar energy -- and feed that energy back into the car and the electric grid. The end result is a more fuel-efficient car that can also lower your home's energy bill.

Google's hybrid, which requires more sophisticated batteries than those used by conventional hybrids, is not the only one of its type. Conversion companies exist that, for several thousand dollars, will turn your Prius or Ford Escape Hybrid into a plug-in hybrid. Others sell do-it-yourself kits over the Internet, though a significant amount of automotive expertise is recommended. This is not a recent phenomenon. For decades people have been creating their own electric, solar-powered and hybrid cars and modifying existing cars to go 100 miles per gallon or more (recently the Honda Insight has proved a popular choice).

So Google's trying to reach the 100-mpg threshold and many other organizations and amateurs are as well, but is 100 mpg feasible without an expensive conversion kit? Let's find out.

The Automotive X Prize

The Tesla Roadster is a high-performance electric car that may rival future 100 mpg cars. Its manufacturer claims it can travel 100 miles for much less than the price of a gallon of gas.
The Tesla Roadster is a high-performance electric car that may rival future 100 mpg cars. Its manufacturer claims it can travel 100 miles for much less than the price of a gallon of gas.
Image © 2007 Tesla Motors, Inc. All rights reserved.

Creating a 100 mpg car is actually quite easy. Engineers have designed vehicles that were capable of several times that amount. The problem is that those vehicles could barely qualify as "cars," much less a vehicle that can take a family of four to the movies. Many of these vehicles also use very expensive materials. That's the real challenge: creating a consumer-friendly car that's attractive, reasonably priced and capable of going 100 miles on a gallon of gas.

To that end, the X Prize Foundation recently announced the Automotive X Prize. You may remember the Ansari X Prize, won by the SpaceShipOne team. The Automotive X Prize is a contest to build a "production-ready" four-passenger car that could be profitable to produce on a wide scale [Source: Edmunds]. The car has to be capable of 100 mpg and has to win a series of races. The prize is expected to be up to $25 million, though some participants, especially those backed by corporations or prominent entrepreneurs may spend even more than that on their contest entries. The Automotive X Prize allows participants to use several different types of fuel, so some teams might be using natural gas, ethanol, diesel or electricity.


Given the designs that are already out there and's success with its Prius plug-in hybrids, multiple teams could feasibly break the 100 mpg threshold. To do it, they'll have to improve fuel efficiency, which means cutting weight. Strong, lightweight materials such as aluminum, carbon fiber and magnesium can lighten the car's body, electronics and wheels. (Some of these materials, like carbon fiber, can be expensive, so the team has to remember that this car must be profitable to produce and market.) Glass actually adds a lot of weight to a car. Types of lightweight glass and composites are being developed, some of which might make their way into Automotive X Prize cars.

Resistance is another key feature for fuel efficiency. Aerodynamic design and low-resistance tires can decrease drag, though those tires can decrease handling. Finally, improved insulation would reduce the need for heating and cooling systems, which would cut down on weight and save gas, though the Automotive X Prize requires entrants to have some sort of air-conditioning system as well as a stereo.

The Automotive X Prize will release its final rules this summer, designs will be reviewed next year and the final batch of races will likely be in mid-2009. While you're waiting for your 100 mpg car, keep your eye on the efforts of Google, the EPA's hydraulic hybrid, the Tesla Roadster and the many researchers, entrepreneurs and amateurs who are looking to create the next generation of ultra-high-mileage cars. It seems Detroit has caught up as well: Google reports that no less than seven automakers are researching plug-in hybrids.

For more information about fuel efficiency, hybrid cars and related topics, check out the links on the next page.

Related HowStuffWorks Articles

More Great Links


  • Alvarez, Cesar. "Ford Model T." Top Speed. Apr. 16, 2007.
  • Baker, Billy. "The Race to 100 MPG." Popular Science. Sept. 2006.
  • Carney, Dan. "Autmotive X Prize Seeks 100-MPG Car." May 20, 2007.
  • Hargreaves, Steven. "Google pushes 100-mpg car." June 19, 2007.
  • Shannon, Victoria. "Google jumps into green arena." International Herald Tribune. June 19, 2007.
  • Stewart, Ben. "100 MPG Available Now!" Popular Mechanics. July 18, 2006.
  • Ulrich, Lawrence. "All Amped Up." Wheels. New York Times Blog. Apr. 20, 2007.
  • "Inventors to race for millions in auto-efficiency prize." May 29, 2007.
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  • "Automotive X Prize." X PRIZE Foundation.