how about bring in the oil, merchants would pump it like they do mining in
some way, and it would be needed as ingredient for some stuff, and tinmen
would need it, drink it or oil themselves or they would start moving with a
delay because of rusting joints. Torches would work better if made with some
oil wrapped on em, or lanterns which could be filled with it. then you could
get a new material from it too, plastic and so, to make items from, toys for
those poor three legged centaur orphans and handless barsoomian babies..