GK sounds like you're duplicating our trip. We just got home this last Monday from a 3 week (6500 Mile) trip with our 2003 Trail Lite B+ . Ours has the 5.7 Chevy motor. We went to Yellowstone first and arrived in a snow storm. Original plans called for Glacier and Baniff Jasper but after the snow headed south instead. Hit all the National parks in Utah and did both rims of the Grand Canyon. Came back east on I-70 thru Vail, Denver and over the Rockies. Avg about 12.5 mpg for the whole trip. Trail Lite ran great and we had a ball with it. Waiting to get out again with it in a couple of weeks.