"....I'm at a loss for why someone who couldn't stand the thought of putting
propane or butane in the system would happily put methane in instead.
It's just as flammable...."

Yeah, not to mention sitting directly on top of a dozen gallons of explosive
liquid, with poisonous coolant circulating under pressure right in front of
you.

Just about everything in the van will burn/melt/explode.  I suppose the worst
case would be a slow propane leak while the van is sealed up, then a spark
from opening the door would ignite it all.  Doubtful, though.

Bill Marshall
'85 GL Tiico "Pandora"
Aurora, IL