by Steve Holder

Created on: May 26, 2007   Last Updated: November 07, 2008

Hybrid vehicles have two motors. One is a conventional gasoline motor, nearly identical to the engines in ordinary cars. The other motor is electric. Think of the electric motor as a more powerful cousin of the electric golf cart's motor.

The secret inside a hybrid car is how smoothly and seamlessly it switches between using the gasoline and the electric motors depending on which serves you better under different driving conditions.

When you start your hybrid car, the electrical systems power up, ready to feed electricity to the drive motor as soon as you step on the gas pedal. (Oops. I guess we can't call it a gas pedal any more, can we? How about "drive pedal?")

With the electrical systems fired up and ready to go, there is no noise, no sound, no vibration. Other than the ready lights on your instrument panel, you have no other indication that your car is prepared to take off as soon as you give it "the gas." When you press on the pedal, electricity from the car's batteries is fed to the electric drive motor and off you go.

If you're pressing hard on the drive pedal to get up to traffic speed, the vehicle's electronics ignite the gasoline engine, bring it up to your drive speed, then transfer drive power over to the gas engine. The electric motor smoothly disengages, and you now have all the highway acceleration of your fossil-fuel-burning kin.

At cruise speed, if the vehicle's electronics calculate that the electric motor can sustain your travel, the gasoline engine is shut down and electric motor takes over.

This switching back and forth between the two motors occurs as often as necessary to ensure you have the power and acceleration you need when you need it, but without burning gasoline if it's not necessary.

Another feature of hybrid vehicles is that when you're slowing down, the car's electric generator engages with the wheels, so the wheel rotation turns the generator to create electricity to recharge the battery. This creates a drag on the wheels helping to slow you down while recharging the battery at the same time. Slick, eh? It's called "regenerative braking."

The other fuel-economy advantage of the hybrid is that when you're stopped at a red light, the gas engine shuts off automatically and is not needlessly idling. As soon as you press on the drive pedal, the electric motor gives you a push while the gas engine fires up and takes over as needed.

Strangely, most present-day hybrid vehicles don't get spectacular gas mileage. They're in the 30-40 mpg range.

Seemingly stranger, hybrid vehicles get MUCH better gas mileage in city conditions than in highway conditions. A typical figure might be 34 mpg city, and 30 mpg highway.

But when you think about it, highway cruising generally uses the gas motor more, while city idling and slow speeds take more advantage of the electric motor. So it ultimately makes sense.

Learn more about this author, Steve Holder.
Click here to send this author comments or questions.