I know because I've done my research, that a common problem with these cartridge filters is putting the o-ring in the wrong spot. That nice snug notch at the bottom of the cap is not where it goes, instead it goes above that in a shallow notch that is way to big for the o-ring. When I first changed the oil it was sitting in the nice snug notch at the very bottom, I had no leaks. I put the o-ring back into that notch and had no leaks until about 1500 miles later when it started pouring its oil out while running. I about dumped my entire oil pan into the snow waiting for it to heat up. I could visually see that the o-ring had popped out and was poking out of the cartridge. So I went and bought a new filter w/ o-ring and installed it in the same spot and it leaked instantly. So I moved it up where it's supposed to go, and tightened it down and noticed that it just flops down to the same notch anyhow. I held it with my finger as good as I could and it did stop leaking until about another 1500 miles. Rinse and repeat. Why is my Volvo forcing me to change my oil every 1500 miles? This is very annoying.

 

Have you bought a new one and installed it in the correct spot? If you install it in the wrong spot and tighten the housing and then loosen it to move it, you can damage the o-ring.

I've done thousands of oil changes and have not had an issue. Remove the old o-ring, install a new one. Lube it and reinstall housing. Works every time.