If enough people do it, it adds up. If you continuously tried to push it at least a couple more days before using your car, over a year that would add up to a couple less tanks of gas. In a nation of 280 million cars, that uses about 340 million gallons of gasoline a day, you could easily carve off a couple of weeks there. Might not seem like a lot, but that's 56 million tons of CO2 not released into the atmosphere.