I Have seen some pretty outragous pump prices. This year diesel for 4.29 at the North Rim. When it was under 2.00 back home. Savings can add up really fast.
I do not get the argument about paying for fuel you don't need.... There is no law that states one MUST fill the extra tank. Use your head, If you are going to be around home for awhile, don't fill it... If you are going on a trip where the conveinece and /or pricing would make it better to fill it...Do so. If you miscalculate and return from a trip with extra fuel....Well you won't need to buy any for awhile, and the bonus is you likely got it at a good price. Unless being temporairily out a 100.00 or so would cramp your style, there is no downside... If that amount of money will cause you to lose sleep at night, then RVing probably isn't for you.