For many years I chased the better gas mileage when towing. Then I decided to sit down and do some hard calculations. If you take into consideration the savings back at home while you are gone for 4 days you may find that the gas cost at 8MPG isn't really that bad. Especially when you add in the fun factor.
Take a look at the savings in electric, water use (if you pay for water), entertainment (movies,dining out,amusement parks fees..etc), heat or Air Conditioning and other expenses you would have if you stayed home.
The fun factor is priceless. You can always find a way to pay for the gas and camping fees. We used to not eat out for a month so we would have extra gas money to go camping during the following month. Don't miss out on the fun.