A miniature filter test has been devised to monitor gasoline streams in the refinery and to insure the quality of the finished gasoline. This filter test has been tied in with road performance. Materials, such as alkyl sulfonates and sulfates of varying molecular weights have been identified in the alkylate process. These same materials have been found on plugged automotive gasoline filters obtained from the field. If gasolines are properly processed and good housekeeping is maintained, quality fuels can be produced that will not plug automotive gasoline filters.