5k on the STP extended life, 8k on the Wix, 10K on the Boss. Have to say I'm kinda surprised with the quality of the Chinese made STP. Pleat spacing is tighter than both the others (Purolator is full synthetic though), media ends are metal crimped together, can was strong and uses coil spring. Only thing that felt cheapo was the drain back valve despite being silicon. Purolator Boss looked great too. Not a fan of the bent metal spring design. Wix was okay too but pleating was wider spaced, didn't stay as uniform, no metal crimp on media ends (not that it seemed to matter. cant even find where media ends mated) and can felt flimsiest of the 3.However bypass and drain back valves both of superior quality compared to the other two (and location for bypass valve. On the intake side). This is a common Ford/Jeep application (Motorcraft FL1A cross reference): Wix 51515, Purolator Boss PBL30001, STP S8AXL. And yes I realize they are different class of filters they just happen to be the last 3 filters I used. Currently have a Mobil 1 filter that I'm going to leave on for 10k miles.
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