The purpose of this method is to evaluate the tendency of an oil to form deposits in the exhaust system of a two-stroke 50 cc engine.

This method is also able to assess the tendency of an oil to cause piston ring sticking and to form varnish and deposits on the piston and inside the combustion chamber, as well as difficulties with the spark-plug, i.e. bridging and whiskering. The rating of the cleanliness of the components, and consideration of spark-plug difficulties attributable to the oil, make it possible to differentiate between two oils having the same performance with respect to obstruction of the exhaust system.