Agree with Sue. Fuel should be the least of expense worries. The Canadian component of the Alaskan trip is huge. Stay out of the restaurants. An hour in a restaurant is the better part of a day worth of fuel. Stay out of private CGs at $35 plus a night. The northern experience is in the PPs at $12PN. The world will survive without you being being in comunication for a few days via WIFI or cellphone.
The trip north is all about what you see out of your vehicle windows but you must slow down to see stuff. The real bears are there hiding among all those rock bears & stump bears.