5.1 Test Method—It was determined through field testing that intake valve deposits could adversely affect the driveability of certain automobiles. Southwest Research Institute and BMW of North America (BMW NA) jointly conducted testing to develop this test method to determine an unleaded automotive spark-ignition engine fuel's propensity to form intake valve deposits. This testing concluded that if an automotive spark-ignition engine fuel could keep intake valve deposits at or below a certain average weight per valve at the end of mileage accumulation, then that automotive spark-ignition engine fuel could be used in the BMW vehicle-engine combination for a specified period without intake valve deposits causing driveability degradation. Minimizing intake valve deposits may be necessary to maintain vehicle driveability and tailpipe emissions control.
5.1.1 State and Federal Legislative and Regulatory Action—Legislative activity and rulemaking primarily by California Air Resources Board and the Environmental Protection Agency necessitate the acceptance of a standardized test method to evaluate the intake system deposit forming tendency of an automotive spark-ignition engine fuel.
5.1.2 Relevance of Results—The operating conditions and design of the engine and vehicle used in this test method are not representative of all modern automobiles. These factors shall be considered when interpreting test results.