Abstract: A fluid filter arrangement includes a housing defining a slot arrangement. A filter cartridge is oriented within the housing. A projection arrangement engages the slot arrangement in the housing and spaces the filter cartridge from a wall of the housing to define a fluid flow path between the cartridge and the housing wall. A filter cartridge includes a tubular construction of filter media and a projection arrangement. A filter assembly includes the filter arrangement connected to a filter head. Preferably, the filter cartridge and filter head are made of plastic. Methods of assembling a filter includes inserting a filter cartridge and projection arrangement into an open end of a housing, engaging projections against through-slots defined by the housing to secure the filter cartridge in the housing. In some arrangements, a filter housing includes a plastic wall having an interior side with a support structure in the form of ribs extending from the interior side of the housing.

Abstract: An apparatus for measuring the differential pressure of fluid in filter. The apparatus comprises a housing defining a pressure chamber. A differential pressure gauge divides the pressure chamber into first and second fluid chambers. The differential pressure gauge is arranged to measure a differential pressure between fluid in the first chamber and fluid in the second chamber. The differential pressure gauge has a variable output.