I can't remember but do the older 250s take speed and odometer readings from the front wheel or the countershaft? Just wondering since that would make a difference in "perceived" mpg. Also, his tire change will also make a difference in his odometer readings. To be honest, I thought that this was a joke and that was the punchline. I don't have the math skills to calculate how big a difference his tire swap will make but it's probably significant.