On previous long tours I have simply driven up to a gas station in a small town and asked if I could leave my truck somewhere for the summer. I usually get strange looks but most of the time they say something like, "Just pull it into the field and leave me the keys in case we have to move it." When I get back I usually ask them to change the oil and/or do a tune-up. Of course, my truck is a 1985 Ford F-150 that doesn't mind being in a field all summer.
If you are doing a short tour, most stations will let you park in back - usually for a small storage fee per night. That way your vehicle has some supervision while you are gone. I find that loops are best, but if you don't want to do an up and back trip - try to find a place with public transportation. Barring that - you can try hitch-hiking - but it isn't what it was 25 years ago. You might not get picked up at all.
Best - J
PS - Try rethinking up and back trips - - you see a different world on the way back because you are going in the opposite direction - - plus the weather may be different - - you'll probably be more observant for little things you missed.