Just my two cents worth, but I think it's dangerous to be running your
fridge on propane while in route. While you may be able to go 99 out of a
100 times without a problem, if you were to get in an accident, you risk
your life. Consider as well that the van is supposed to be level when
using propane. Are you driving through Iowa? If not, then that's one more
reason not to be using propane. It's pretty common for the flame to go as
as well.

12 Volt operation works just as well as AC or propane. I have links where
one person did the testing. Second, it's free and safe, so why use propane
while the van is moving? It's also a lot easier to light the fridge on
propane when it's been running for a while either on AC or 12 V, and
that's an added plus.

The only drawback I see is when you stop the van, for gas or picture
taking/whatever that can disrupt the cooling cycle and lessen the
efficiency.  When I put in my auxiliary battery, I wired the fridge up so
that it would not shut off to prevent this.

About the only drawback, is it's easy to forget the fridge is on 12 V, so
some kind of a visual reminder is a good idea.

Troy