Today, we posed a question on the front page of the Wall Street Journal:  How much of a gallon of gas is lost to heat, friction and other factors in a vehicle instead of actually being used to power the wheels?

If you haven’t already seen the answer we gave in the ad, you be might be surprised. Your car only uses 20 percent of each gallon of gasoline to actually get you where you want to go — the other 80 percent is lost due to various sources of inefficiency throughout the car.

Aside from being an interesting trivia point, why does this matter? Because improving the efficiency of our cars and trucks is a practical step we can take today to save energy and reduce greenhouse gas emissions.

Consider the fact that all forms of transportation account for about one-third of emissions in the U.S. — and emissions from passenger cars, light trucks and heavy-duty trucks make up the majority of that figure.

The good news is that achieving near-term improvements in vehicle efficiency does not require complicated new policy programs or the creation of new financial markets, like cap and trade. And it doesn’t require new taxpayer subsidies.

Instead, we can take advantage of technologies that already exist to improve fuel efficiency — the most cost-effective form of “alternative” energy today for cars and trucks. They include advanced engines and transmissions, as well as improved vehicle designs that help reduce aerodynamic drag, rolling resistance, and vehicle weight. Such advancements can save energy and reduce emissions without compromising safety, handling, or comfort.

Efficiency can be further improved by using advanced powertrains, such as advanced diesel engines and gasoline or diesel hybrids.  These technologies are available today but are generally more expensive than improving efficiency of conventional powertrains.

Lastly, there are breakthrough technologies under research and development beyond advanced powertrains that not only improve efficiency but also diversify transportation fuels, including hydrogen fuel cells, plug-in hybrids and electric vehicles.

For our part, ExxonMobil is advancing technology to improve fuel efficiency in a number of these areas. We’ve developed a variety of technologies available today, such as tire liners that keep tires inflated longer, advanced fuel economy engine oil, and lightweight plastics for use in bumpers, fuel tanks and other car components. These seemingly small advances can make a big difference when applied to the millions of cars on U.S. roads. In fact, using technologies such as these in one-third of U.S vehicles would translate to a savings of about 5 billion gallons of gasoline and greenhouse gas emissions savings equal to taking about 8 million cars off the road.

We’re also progressing next-generation vehicle technologies. For example, we have developed advanced polymers for lithium ion battery separator films that could help enable the next generation of hybrid electric cars. We are researching a way to generate hydrogen on board vehicles to power fuel cells — an effort that could improve fuel economy by 80 percent and reduce emissions by 45 percent. And, we are sponsoring breakthrough research to find out how to scale up biofuels from algae.

Taking advantage of the technologies that can improve conventional vehicles today is the first step we should take to save energy and reduce emissions. At the same time, we have to keep progressing the next-generation vehicle and fuel technologies with real economic promise in the future.