Gasoline engines have their advantages, and perhaps one of their best advantages is the potential to become more fuel efficient as engineers improve their performance. This process will make it harder for other technologies to show a big benefit, said CNNmoney.com.

While smaller gas-powered vehicles currently get 35+ miles to the gallon at highway speeds, only about 15 percent of gasoline’s energy is being used, said CNNmoney.com. Engineers are making changes to gasoline engines to try to use more of gas’s available energy. These changes include modifications to the timing of the sparks, valve openings, and fuel injection.

Some companies are developing homogenous charged compression ignition (HCCI), a process that will allow cars to travel farther on each gallon of fuel. The process is similar to that employed in a diesel engine and could create 15 percent better fuel economy.

Using electricity to power more systems within the vehicle could add up to 10 percent to a vehicle’s fuel economy, said CNNmoney.com. If electricity can be used to power the car’s wheels for short drives, the gas engine can be saved to power longer trips.

Ford and GM have created range-extended plug-in vehicles that have hydrogen fuel cells instead of internal combustion engines to generate additional power. Hydrogen fuel cells will soon be commercially viable, said GM.

One drawback to alternative fuel vehicle is that their power sources require tanks or batteries that are much larger than a gas tank. One of the benefits of a gasoline engine is that its tank is “right-sized.”