I agree with Mountaineer42 on the route from MX 15 to San Blas, I have lost marker lights on both occasions going that way. My 2006 Ram3500 CTD gets about 11.5 mpg towing the trailer and I have no problem, we usually spend a couple of nights in Punta Cerritos RV park in Mazatlan, and I go into one of several big Pemax stations going south through Maz, and don't even get down below the worry point before we get to Tepic. We are planning leaving Lukeville on 25 Oct, stopping in Santa Ana, Guaymas, and Los Mochis one night each, and two nights in Mazatlan, then to La Peñita. We don't overnight in Pemex any more as we both need electric hookups for our CPAPs. We have stayed overnight at Pemex 4006 outside of Culiacan Sinaloa several years ago, and for 50 pesos the armed guard parked us by a light pole that had a 15 amp plug in. We felt pretty secure that night guarded by Jesus with an M16. I always try to diesel there at 4006 and take a lunch break as we do like the food in the restaurant.