Audi Repair: 2001 Audi A4 Quattro Sedan 2.8 V6 engine, audi a4 quattro, castrol gtx

Question
Is there a certain type of oil filter that should be used?
What about the weight of the oil?  Engine light also on.  Just bought from private owner; fluids low.  Brake light and ABS sporatically comes on and off, check engine light constant.

Answer
I would use a good quality filter, it is not worth saving money on this item!  Now Audi does not make filters, so going to the dealer doesn't pay either, I normally use good quality filters made by Bosch, Mann, Mahle, Hengst for instance.  Regarding oils, if you use synthetic, the engine better be very tight, otherwise you will discover oil leaks you never knew you had.  I normally use a Castrol GTX or other good quality oil of 10/40 or 20/50 multigrade.  The check engine light you can get the codes read out at an advanced autoparts store, check your manual for what oils are recommened, and go with those.  Never be scared to contact the previous owner and ask what fluids he or she used.  Good luck with your new purchase!  Jan