Some people make mistakes when asking me questions.
Father: How far can we go? I don't want to give them any extra fuel when we return the car.
Me: Tell me x, y, and z.
Father: x, y, z.
Me: We can make it to the fuel stop in 120 miles.
An hour and a half goes by, then 45 minutes of worrying-
2 Miles past empty, with a >half gallon left, we made it there!
I don't remember the exact numbers, that was the 2011 NAIAS, but I love those situations! OTHER people start to drive better, when you remind them of factors like average speed, aggressiveness of accelerating, and wasting fuel in general- which may contribute to walking/pushing.