It's a '96 A4 with the 2.8 12v engine. 1. I have no idea what the factory fill was - some say it was a synthetic... 2. The dealer wanted to go with 20W-50 dino oil during the included maintenance, but I brought them 5W-50 Castrol Syntec. I used Syntec for about 90k miles with very good results. The oil stayed clean-looking for at least 7500 miles, and the engine barely burned any oil. I kept the oil topped off with less than 1/2 a quart during oil change intervals. 3. I've been running M1 0W-40 for about 10k miles, and this oil darkens a lot faster compared to the Castrol 5W-50. I also seem to need more oil with the Mobil 1. I've never had an oil analysis done, so I can't say if the "fake" synthetic is possibly better than the real synthetic Mobil. I'm now looking at Amsoil, Neo, and Pentosin 5W-40 as other options.