These websites can help determine gas prices, both in Alaska and en route to and from Alaska, for your RV trip.
Alaska – alaskagasprices.com
British Columbia – bcgasprices.com
Yukon – yukoninfo.com
If you are not sure how much gas you will need, here is a rough guide:
Class A (40-foot bus style) will get 8-13 mpg or 18- 29 litres/100km
Class C (cab-over) consumes 10-15 mpg or 16-23 litres/100km
Class B (van style) gets about 18-20 mpg or 11-13 litres/100km.