HOUSTON - In an 844-mile tour of Texas, a hypermiling expert driving a hybrid Toyota Prius was able to average 68.5 miles per gallon of gas, 49 percent more than the EPA estimate of 46 mpg for the car. On just one tank of gas, the driver was also able to get markedly better gas mileage and use much less gas than a driver in a Prius on the same route, using normal driving habits.