I would always recommend that you store your RV with a full tank of fuel, whether it be diesel or gas. By doing this, you keep your "air gap" in your fuel tank at a minimum, thereby reducing the condensation of water in your tank.
Water in your tank is especially bad for diesels since it makes your desiccant filter fill up faster, plus subject your tank to corrosion. For gassers, the water can lead to tank corrosion plus hard starting and running.
Using SeaFoam or any other type of stabilizer, will help the fuel stay "fresher".
Out West Somewhere
2016 Sunseeker 3050DS towing 2006 Hummer H3