I recently bought a 2002 A6 2.7T without a owner's manual. I'm getting ready to change the oil but I don't know how many quarts. Also, what's the best oil and filter to use? Thanks.

6.0 liters- 5.5quarts to you (aprox)

Use a full synthetic oil, castrol syntec, mobil 1. just make sure it meets vw specs. the oil should say it on the bottle.
a mann filter is a must.

I have a 2000 2.7 and I have to put just under 7 quarts in it. I use Mobil 1 extended performance in a 5W-30 and a Mobil 1 extended performance filter M1-204. Good Luck.

I use mobile 1 0w-40 and Bosch filter 3402. Takes 5.5-6 quarts. I put 5.5 quarts in, fire it up and let it warm up...then shut it off and sit for about 10 min and check the oil level. I usually add another half-quart after that but there have been times it hasn't needed it.

I was told by my indie shop that the Mobil1 filter is better than the Bosch (yeah, I know Bosch is probably the OEM). I'd also suggest you use Mobil1 0W-40 in the winter and 5W-40 or 10W-40 in the summer. You want your oil to be "loose" so the turbos get properly lubricated in very cold weather.

yup, just under 7L

try the Synthec 0-30 .. its underrated by many,,, let me tell you that this oil is better than the Synthec 5-40... just look at the back of the oil can for the specifications... compar every oil you want ..... they said it pass(0-30 Synthec) more standard than any other oil (VW84647......... something like that) ....
UAP NAPA gold filter is a good choice too
and 6.7liters is the exact amount of oil necessery for a 2.7T..

Its just under 7 quarts, 5W 40, I use Motul.

OOOO

No wonder there is some discrepencies, according to Bentley Service Manual, page 03-24, 2.7T engine (A6, S6) > 6.5 litres > 6.9 US quarts.... And from AudiWorld Audi spec sheet, 6 L = 6.3 Quarts.
Just make sure it's to the top of the Fill line on the dipstick and use good synthetic.
Bentley says Audis ship with 0W-30 syn in crankcase, and at next oil change use 5W-30 syn. FWIW.