Many trailhead sites ban RVs. Our Sprinter RV is 26 feet long, 7.5 feet wide, under 12 feet high, and its 3.0L mill gets 17-20 MPG but we can’t take it to many tempting spots. We manage to stand each other in it for months at a time but we always have a home and doctors to return to.
Good off-roading 4WD Sprinter vans are now available but I’m not sure if larger rigs are built on that platform. And I sure wouldn’t want to take anything like that through Fat Man’s Misery or the Turkey Track in Anza-Borrego Park.