for me its about a 7 mile trip from my house to town and its downhill most of the way. so I always put in nuetral and coast. sometimes i even shut it right off. so definitely coast big hills in neutral. and the best thing for gas mileage is keeping her tuned up. new fluids, general maintainence, rotate tires, adjust brakes, blah blah blah. and clean ur throttle body and throttle plate. I did all of this when it was needed bad and i changed my 02 sensors and i gained a lil over 2mpg