As part of the midterm evaluation of the 2022-2025 light-duty GHG emissions rule, the Environmental Protection Agency (EPA) has been evaluating fuel efficiency data from tests on newer model engines and vehicles. The data is used as inputs to an EPA vehicle simulation model created to estimate greenhouse gas (GHG) emissions from light-duty vehicles. The Advanced Light Duty Powertrain and Hybrid Analysis (ALPHA) model is a physics-based, full vehicle computer simulation capable of analyzing various vehicle types with different powertrain technologies and showing realistic vehicle behavior and auditing of all internal energy flows in the model.Under the new light-duty fuel economy standards vehicle powertrains must become significantly more efficient. Cylinder deactivation engine technology is capable of deactivating one or more of its combustion cylinders when not needed to meet power demand. In order to understand and measure the efficiency effects of this technology, the EPA benchmarked a 2014 Chevrolet Silverado with a 6-cylinder 4.3L LV3® engine, capable of lowering its displacement from six to four cylinders.EPA’s complete benchmarking study of this vehicle included both chassis testing and engine dyno testing to measure the vehicle and engine efficiencies. This paper describes the test method and results for the engine dyno portion of the benchmarking. The test method involves installing the engine in an engine dyno test cell with the engine wiring harness tethered to its vehicle parked outside the test cell. This technique enables the engine to be mapped using the stock ECU and calibrations along with all the safety checks including those coupled to vehicle sensors. The data measured included torque, fuel flow, emissions, temperatures, pressures, incylinder pressure, and OBD/epid CAN bus data. The benchmarking test results include engine fuel consumption maps showing the effects of cylinder deactivation technology.