Idling a car is bad for the environment and your wallet. On average, idling your car a few minutes, five days a week can put you back $130 a year. To break it down, a ten-minute idling session will cost you roughly $.50 of gas. This done for five days a week, and $130 poorer you become. In some places, idling is a finable offence, with up to $125 fines.