You're taking interstate highways the whole way; there's going to be gas at regular intervals. I'd be surprised if there's a stretch where gas stations are even 50 miles apart. But as cblaisd said, do watch for the "Next Gas XX Miles" signs in remote areas. And even if you're using a website or GPS to locate stations, consider practicing safe habits such as not letting your gas drop below 1/4 tank unless you know you are going to pass a sizeable town in the next 50 miles. A station listed in the GPS database could be closed for the day or for good.