The apparatus for measuring performance of a suspension for cooling a computer processing unit is a measurement and testing tool allowing for the fabrication of new suspensions, and measuring and testing their short-term and long-term thermal performance in real time on any liquid-cooled computer processing unit. The suspension is prepared in a sample receiving reservoir and pumped across the unit, and then input to an air-cooled heat exchanger for recirculation back to the sample receiving reservoir. Temperatures of the working fluid are measured between the sample receiving reservoir and the computer processing unit, between the unit and the heat exchanger, and after output from the heat exchanger. Pressure differentials of the working fluid is measured across the computer processing unit and across the heat exchanger.