It’s common knowledge that driving aggressively can dent gas mileage, but it’s difficult to determine exactly how much gas drivers waste. A new study by researchers at the Department of Energy’s Oak Ridge National Laboratory has quantified the impact speeding and slamming on the brakes has on fuel economy and consumption. They found that aggressive behavior behind the wheel can lower gas mileage in light-duty vehicles by about 10 to 40 percent in stop-and-go traffic and roughly 15 to 30 percent at highway speeds. This can equate to losing about $0.25 to $1 per gallon.