rejuvenating and or cleaning composition identical to that used in example 1 was added to the vehicle 39 s fuel tank which fuel tank contained approximately 15 liters of gasoline fuel the vehicle engine was then actuated in the normal way by spark ignition thereby allowing the mixture of fuel and cleaning composition to pass into the engine 39 s injection system and to combust in the cylinder chambers the unburnt fuel and gases passing through the catalytic converter the vehicle was driven for a distance of 30 miles at a speed of 50 miles per hour prior to treatment according to the invention the vehicle was driven on a clayton chassis dynamometer system dc500 while following the driving schedules of the us federal test all exhaust gas sampling was carried out on diluted exhaust gases in a dilution tunnel which was designed to fulfil the code of federal regulations 1 the flow of diluted exhaust was 6 m 3 min maintained by a venturi and the average dilution ratio was approximately 10 5 according to the test three gaseous transients were sampled a first u201c cold start u201d transient y ct corresponded to emissions produced upon starting the vehicle from a u201c cold u201d state wherein the vehicle engine had not been used in the prior period of 8 to 12 hours a second u201c mid range u201d transient y s corresponded to the emissions expelled at normal working temperature in the drive cycle while a third transient y ht was sampled upon starting the engine after a 10 minute period during which the engine was at rest measurements of regulated emissions were carried out in accordance.