Engine Test Procedures to Evaluate Octane Requirement Increase and Intake System Cleanliness

As a vehicle accumulates mileage, deposits begin to build up in the intake system. These deposits, especially those on the intake valves, may cause poor cold start driveability, losses in power and fuel economy. Modern gasolines have multi-functional additives to provide all-around performance in areas of detergency, corrosion inhibition, stability, etc. Some of these gasoline additives may inadvertently cause unusually high increases in intake valve deposits and adversely affect the octane requirement of the engine. Dynamometer engine test procedures have been developed to evaluate the performance of gasoline additives in these areas. This paper describes the details of the test procedures, their repeatability and typical test results.