Evolution of the Hybrid
The hybrid is a compromise. It attempts to significantly increase the mileage and reduce the emissions of a gas-powered car while overcoming the shortcomings of an electric car.

The Problem with Gas-powered Cars
To be useful to you or me, a car must meet certain minimum requirements. The car should be able to:

  • Drive at least 300 miles (482 km) between re-fueling
  • Be refueled quickly and easily
  • Keep up with the other traffic on the road

A gasoline car meets these requirements but produces a relatively large amount of pollution and generally gets poor gas mileage. An electric car, on the other hand, produces almost no pollution, but it can only go 50 to 100 miles (80 to 161 km) between charges. And the problem has been that it is very slow and inconvenient to recharge.

A driver's desire for quick acceleration causes our cars to be much less efficient than they could be. You may have noticed that a car with a less powerful engine gets better gas mileage than an identical car with a more powerful engine. Just look at the window stickers on new cars at a dealership for a city and highway mpg comparison.

The amazing thing is that most of what we require a car to do uses only a small percentage of its horsepower! When you are driving along the freeway at 60 mph (96.6 kph), your car engine has to provide the power to do three things:

For most cars, doing all this requires less than 20 horsepower! So, why do you need a car with 200 horsepower? So you can "floor it," which is the only time you use all that power. The rest of the time, you use considerably less power than you have available.

Smaller Engines are More Efficient
Most cars require a relatively big engine to produce enough power to accelerate the car quickly. In a small engine, however, the efficiency can be improved by using smaller, lighter parts, by reducing the number of cylinders and by operating the engine closer to its maximum load.

There are several reasons why smaller engines are more efficient than big ones:

  • The big engine is heavier than the small engine, so the car uses extra energy every time it accelerates or drives up a hill.
  • The pistons and other internal components are heavier, requiring more energy each time they go up and down in the cylinder.
  • The displacement of the cylinders is larger, so more fuel is required by each cylinder.
  • Bigger engines usually have more cylinders, and each cylinder uses fuel every time the engine fires, even if the car isn't moving.
This explains why two of the same model cars with different engines can get different mileage. If both cars are driving along the freeway at the same speed, the one with the smaller engine uses less energy. Both engines have to output the same amount of power to drive the car, but the small engine uses less power to drive itself.