We have the Good Sam Rand McNally which we purchased after squeezing back through a tunnel on a road we shouldn't have been on. Just enter the size of your rig, your tanks, your propane, your weight, and it will not steer you wrong. It lists campgrounds, gas stations, rest areas, Walmarts, all the the touch of a few buttons, and will calculate your mileage with every fill up. Even knows what gas station you're at! Love it!