BTW. your assumption that the pressure from each feed is the same. It's not. Also consider the FACT that somewhere in that pipe there are two different columns of oil meeting. That point can move back and forth in the pipe as the local pressure changes. Pressure and no flow. It happens.
Your very close on the column of oil. A column of oil has hundreds of columns within the column of oil going in different directions some going sideways some going back or forth some going up or down. It is not just all the oil gushing forward.
