Fuel efficiency and good gas mileage are important to the environment for many reasons. Burning gasoline to power your car emits a lot of CO2, which contributes to climate change, so using less gas decreases your emissions. Also, oil is a non-renewable resource, so using less of it helps to sustain the amount that we have today, and gives us time to come up with alternatives. Driving a car that has good fuel efficiency helps to use our resources in the most sustainable, responsible way. (Source: Fueleconomy.gov / Photo: Flickr)