We are investigating feasibility of a buried 6oil pipeline. Given a maintenance temperature of 130-160deg F, i am concerned that the fluid will "set up" when not in use (matter of days). Is this an issue - if so, what is the preferred method to avoid this set up -- line flush after use (potential high costs in flush fluid for a multi-mile pipeline), pig thru the line after each (again, need some motive power for pig, seems cost-prohibitive), steam or electric trace. Or is this a non-issue since it'll be buried 4-5ft in fairly warm climate.