Filter insert with improved filter performance under operating conditions

A filter insert for a fluid filter device, comprising:

• a) a circumferential first filter element comprising a folded first filter medium, b) a circumferential second filter element comprising a folded second filter medium, c) a first base element and a second base element, and d) a cover element with a fluid outlet,
• wherein the first filter element, the first base element, and the cover element form a first inner chamber, said second filter element being arranged in the first inner chamber, and the second filter element, the second base element, and the cover element form a second inner chamber,
• wherein the distance between the first base element and the second base element in the axial direction is in the range of 0.1*L1 to 0.6*L1, wherein L1 is the length of the first filter element in the axial direction,
• wherein the filter insert is designed so that a fluid to be filtered can flow from the outside through the first filter element into the first inner chamber, from the first inner chamber through the second filter element into the second inner chamber and out of the second inner chamber through the fluid outlet,
• wherein the quotient of the accessible filter surface area of the first filter element divided by the accessible filter surface area of the second filter element is greater than one,
• wherein the quotient of the filter rating of the first filter medium divided by the filter rating of the second filter medium equals one or more, wherein the filter rating is the filter rating determined according to ISO 19438:2003-11 for the overall separation efficiency, wherein the first filter medium has a bending strength according to DIN 53864:1978-08 of 10 N*mm2 or more, wherein the bending strength is determined with a bending angle of 5°,
• wherein the second filter medium has a bending strength of 2.5 N*mm2 or more according to DIN 53864:1978-08, wherein the bending strength is determined with a bending angle of 5°, and
• wherein the quotient of the bending strength of the first filter medium divided by the bending strength of the second filter medium equals one or more.