Road trip next year - car or van?

The van has been winterized, tarped over (it still leaks around the bed windows *sigh*, with a 1W solar panel (paid $5 for!) plugged in for the starting battery's benefit. (The house batteries get power from the big solar panels on the roof) I considered just putting a jumper wire between the battery connectors on the battery isolator, but I figured 1W is enough to keep it topped off with zero usage. The in-dash stereo's memory runs off of the house batteries due to the custom wiring installation I did on it.

Now to the topic at hand ...

I am planning for a road trip around the middle of next year in my car since the trip will be at least 4,500 miles round trip. Even though gas prices have dropped by about $2/gal since March 2014, it would still cost a good $1400-1500 in gas round trip based on 9.5mpg average. The car gets about 30-35mpg, so figuring 32mpg average, the cost would be about $425-450. I would require campgrounds more likely unless I simply recline the car seat and sleep that way, or pitch a tent at campgrounds.

Where comfort is concerned, the van is be better but cost wise, the car wins out. But who knows? I might change my mind in the next 6 months and just pay the $1500 in gas since I want to make it a long, drawn out trip of several weeks, if not an entire month or longer.