Mileage increases town verses highway?

by Mike Marinelli
(Renton, WA USA)

It is my understanding that the best mileage increases are with town driving, and not so much with freeway driving. I was told that the generators only produce so much hydrogen, and it can't fully keep up with freeway drivinmg. I ask because I drive 272 miles a day in a Ford Ranger 95% on the freeway.