From experience 468 miles out of a tank is possible with a 1 gallon reserve. But you have to be above 6k feet and go no more than 45mph with slow leisurely acceleration. At normal speeds 65-75 I have seen up to 20mpg but it was all above 5k feet.

Not a normal thing but it is possible.

When I was stock I have seen 300+ miles out of a tank while in the lowlands at highway speeds.