A dynamometer comprises a frame, an inertial flywheel, and a starter motor. The inertial flywheel is supported by the frame and the starter motor is movably mounted to the frame so as to be selectively engageable with the inertial flywheel. Means is provided for coupling an engine to be tested to the apparatus. The flywheel is brought up to speed by means of the starter motor and then coupled to the engine, which has been separately brought up to speed, via a clutch. The flywheel is supported by the frame in pressurized oil sleeve bearings.