When you buy a new or used car, you may be more worried about the gas consumption than you ever were in the past. With gas prices hovering near three and four dollars a gallon, depending on where you live, you want to make the most of the money you put into your gas tank each time you fill it up - if you can afford to fill it up at all. This is when you should pay close attention to the estimated gas mileage of the cars and trucks you are considering for purchase. The key word there is estimated. If you have had your car or truck for a while, you may have dug out your manual to see what your estimated gas mileage may be at the present time.