The RV Plus card is great. If you get a lifetime membership to Good Sam Club, you never have to worry about renewing, get $0.08 off of the cash price at the pump, the card will activate the pump (you don't have to go in), and you get $0.10 off of each full gallon of propane (partial gallons are NOT discounted).
If you buy 6.00 gallons of propane, the discount is $0.60, 6.97 gallons of propane, the discount is still $0.60, 7.00 and the discount is $0.70. You also earn rewards points, and if you register the rewards portion of the card, you get 5 free drink refills (as of a couple of months ago anyway).
They may cost a little more than a local, off the main road station, but can you get into the local, off the main road station?