Read your owner's manual carefully before you change the oil and oil filter so that you understand every step of the procedure. I recommend you pickup Subaru OEM oil filter from your local dealership as it will include the new crush washer for the drain plug. For every oil and filter change, you have to replace the washer on the drain plug. Here are some things you will need:
-Ramps to get the car up in the air (such as Blitz Rhino Ramps) or a jack stand.
-1 or 2 drain pans.
-Oil filter wrench to remove the oil filter.
-Torque wrench to remove the drain plug.
-Socket/ratchet wrench set and a torque wrench.
-Replacement oil filter and crush washer/crush ring.
-Replacement oil filter.
-4.2 quarts of 5W-30 conventional or synthetic (or synthetic blend) motor oil.
Here are third-party oil filters which fit our cars:
-Mobil 1 M-108
If you are going to use an aftemrarket oil filter, then you are going to need to purchase the crush washer separately. Don't quote me on this, but I am PRETTY sure that our crush washer size is M20.
I intend to do a full DIY with pictures and video for the 08 WRX when it comes time for my next oil change (which is 2,000 miles from now, sorry!).