The cost of gas is nothing compared to the cost of daycare.
That is without question the biggest change in our lives over the past year. We still use the RV, and it saves money or at least breaks even with getting a hotel. There's no way we'd be able to take the baby, all his stuff, all our stuff, and a boat for a weekend regatta with just the Explorer. Oh yeah, we need to take a babysitter (and all her stuff) this year too.
Since the Explorer only gets 15 MPG towing, and the RV gets 7 MPG, the impact really isn't too bad.
Mike