I won't use the red filter on anything. Too course of filtering and have had enough debris get through to hold the float valve open. White for gravity flow systems, and the 40 micron 84001895 for fuel pump systems. Or the 12 050 01-S for larger engines.Well, according to Briggs the Red Filters are for gravity feed and the white filters are for engines with pumps, however i've had no issues with using the white filters on gravity systems.