The mixture of the fuel is not a big deal since trucks are coming out with computer controlled fuel systems. They will compensate for fuel mixture the keep the truck running clean just as a cars compensate for the pecentage of alcohol in the fuel. I think that fuel quality has been blamed over the years for LPG fuel system problems. It was usually worn out parts in the fuel system. I have never taken apart an LP regulator with more than a couple thousand hours on the truck and not dumped the oil out of it. I may be wrong, but I always figured the oil was normal since LP gas is a by product of oil refineing. I just figured there is always going to be some oil left in the fuel.