I tried a lien where i supply one refinery from an oil rig, and it went just fine. THen i tried supplying a second refinery from the same il fiel and eventually both busineses dried up. The refineries never reched full potential, despite having more than enough demand, and both supply lines are well under the 20 minute rule.
the bug is: if i supply just one (either one) refinery with one oil field, it works. if i try to supply both of them, the economy evenutally collapses.