Even with a fuel gauge and without a fuel petcock, I still zero my trip meter every time I fill up. It helps me keep track of my gas mileage, but also lets me know when I'm approaching the limit of my fuel. When I hit 180 miles, I'll file away that I need to refuel soon. When I hit 200, I look for the next available gas. Even at 200 miles, though, I have at least a half gallon left, which is another 20+ miles. Still, I don't want to push the thing or call AAA if I don't have to, so I try to be conservative.