I've run several stories lately on hybrid vehicles -- comparing their costs against traditional gasoline engines (http://askpatty.typepad.com/ask_patty_/2008/04/pros-and-cons-o.html) and giving tips on how get the best fuel economy when driving them (http://askpatty.typepad.com/ask_patty_/2008/04/tips-to-get-bet.html) - and it occurred to me that it might be helpful to explain what makes these powertrains so different.

Now that gas prices are hovering around $4 a gallon, many drivers are becoming more aware of their need to cut their gas costs. And with Earth Day upon us, we've been bombarded by messages telling us to make greener choices to help save our planet.

Have you heard of "Hypermiling"? Hypermiling is a method of driving your car in a manner that maximizes mileage, and it can be done in any vehicle regardless of whether it has a hybrid or traditional gasoline powerplant. Hypermiling has become a popular technique among drivers worldwide, especially as concerns over increasing gas prices and environmental issues heighten.

With all the talk we’ve heard lately about sustainable eco-friendly vehicles, I thought it might be useful to identify some pros and cons of the alternative engine choices available now and promised to come to market in the future.