Fuel-efficient cars

There are cars out there that get good mileage per gallon (i.e. small cars) and i am looking for one that will get me around 40 mpg such as these cars.
Here's why I want to buy a fuel efficient car:
1) I don't want to buy anything that will increase global warming.
2) I also wouldn't mind saving a whole lot on gas money. Think about how much average gas money a person spends in a year. If you spend $200 a month on gas, that is $2400 a year. If you buy a car that costs, $25,000. You will double that amount of money if you drive the car for 10 years...meaning that you will be essentially paying $50,000 for a $25,000 car.
If you double the amount of mileage per gallon of gas, you halve the amount of money you spend on gas every year. Pretty smart when you think about it!