An automatic oil additive injector is disposed over the drain opening in a bottom wall of an engine oil pan and extends into the oil pan. A side port is provided in a housing of the injector for allowing oil to drain therethrough when the oil drain plug is removed. Primary and secondary valve assemblies...http://www.google.es/patents/US5327861?utm_source=gb-gplus-sharePatente US5327861 - Automatic oil additive injector
