Kind of makes 62.5 MPH seem like a good compromise doesn't it?

It also shows the penalty we pay for weight, something I know from flying. Unlike in the bus where power varies, in the plane I set the power and leave it. There are two factors that influence speed, one being altitude where I gain 1.4 knots for every 1000 feet of altitude and the second is weight, where I gain about one knot for every 100 pounds of fuel I burn.

On our buses if we can reduce the weight of the bus and tow vehicle we will increase our mileage. Also, our fuel mileage increases in warmer temperatures because the air is thinner and thus less resistance to the frontal area which is akin to flying in thinner air at higher altitudes and getting more speed.