This paper describes a method of using the total emission concept for conveniently assessing the accuracy of emission measurements. The measured total HC emissions are treated as unburned fuel (C8 basis) plus burning zone HC (C1 basis). Statistical analysis shows that the emission test data may be questionable if the total emission calculation exceeds the range of 100 +/- 2σ*. This paper also describes a technique to determine the Air to Fuel (A/F) ratio for two-stoke engines. This method may be used to calculate the overall A/F and burning zone A/F for DI two-stroke engines and for engines using oxygenated fuel.Twenty-five OMC engines have been tested by following EPA emission test procedure. The total emission and A/F analysis for these tests indicate that the new method is a very useful tool for assessing A/F and the accuracy of emission measurements. This technique reduces the emission test errors and shortens engine calibration and development time.