If you are heading out for a driving vacation this July 4th, here are a couple of tips that can save you gas money. Roll up your window and turn on the air conditioning. Back in the day air-conditioning really hurt a car’s gas mileage, but no more. Air-conditioning is very efficient now. Now that you have a cool ride, slow down. For every 5 miles per hour you go above 60, you pay an additional 24 cents for gas. Even a cruise up to Tahoe will cost you quite a bit more if you lead-foot it.