Abstract: An apparatus for measuring the quantity and flow rate of liquids in a flowing fluid stream containing liquids and gases such as found in oil well production, with an optional controller for oil well pumps to control the pumping period or speed based on pump displacement. Total number of tank fill events provide a precise measurement of total volume. Volumes are accumulated on a time base to determine flow rate and on the basis of strokes to determine pump displacement. Liquid measurement is accomplished without restriction to the flowing stream, even in the event of a valve failure. The filling of each tank with oil of low or high viscosity can be measured by level, hydrostatic pressure, or weight sensors. Measurement of total produced volumes are accumulated with the accuracy and repeatability needed when correlating producing wells with injection wells, and when diagnosing well problems.