A radiotracer method for measuring engine oil consumption, using tritium as the tracer element, has been adapted for use in both gasoline and diesel engines. The method is rapid, accurate, versatile, and almost totally free from radiological hazard. A digital computer with plotter has been programmed to produce a unique oil consumption “map” over the effective engine operating range. Such a map will indicate at a glance the areas of operation requiring improvement from an oil consumption standpoint. Some interesting observations have also been made of transient oil consumption phenomena.