Cold-cranking simulator simulates rheological process of "an average engine" during cold starting. The engine's starter motor was replaced with a small series wound universal motor, a typical sewing machine motor, and the engine, with a specially designed cold cylinder and an insulated cylindrical rotor with a pair of parallel flats. The sample oil is continuously sheared under a periodically varying shear rate, lower when the flats pass. Oils in real engines are similarly sheared, high in the journal bearings, oscillatory on piston rings and low in galley. Most developmental work went into proper sizing of the flat to simulate relative shear rate distribution in an "average engine". Both an engine and simulator is calibrated with a set of Newtonian standard crank case oils with known viscosities.