SubaruXTWiki
HowToChangeYourOil

You should change your oil once every 3,000 to 5,000 miles. (Is that right?)

  1. Lift the front end of the car, or drive onto ramps
  2. Remove the oil cap from the top, center of the engine
  3. Put a 2-gallon container under the oil pan
  4. Remove the old oil plug from the oil pan
  5. Wait 15 or more minutes for the oil to fully drain

Meanwhile, change the filter:

  1. Unscrew the old filter using a filter wrench if necessary
  2. Check that the old filter gasket is not hanging off the pump still
  3. Dab some fresh oil on your index finger and rub it around the gasket on the new filter
  4. Screw on the new filter

Finish changing your oil:

  1. Replace the oil plug and tighten to torque spec
  2. Add 4 quarts of new oil if you have an XT or XT Turbo, 5 quarts if you have an XT6(see ShouldIUseSyntheticOil)
  3. Replace the oil cap

The last straw:

  1. Lower the front end of the car
  2. Start the engine, let it idle down to normal
  3. Check for leaks while car is running.
  4. Check the Automatic transmission fluid level if equipped(and warm)
  5. Shut engine off and wait ~ 1 minute
  6. Verify engine oil level

I change my synthetic oil once every 10,000 miles. –cvk

Additional Info:

Research paper help : Why regularly change oils