I have created a MPG tool, which also aims to show the cost in dollars of commuting to work by car. It also shows how such gasoline consumption affects the CO2 levels in the atmosphere, your “carbon footprint.” A gallon of gasoline weighs about 5 pounds, but puts off 20 pounds of CO2 when burned!!! (How? A molecule of unburned carbon-based gasoline has an atomic weight of 12, but when it is burned, it attaches itself to two Oxygen molecules (atomic weight of 16 each) and CO2 thus weighs in at 44 atomic units.) I thought this would be an interesting tool. You can see how many olympic-size swimming pools of CO2 you create every day, every week, every year. Keep checking back, and I will update it. Special thanks to George Mav at mavaction.com for the brains behind the tool.