Have just bought a 2001 A6 Avant 2.5 Tdi. It's done 70k miles, and has had the long services from audi - one at 22k miles, and one at 54k miles in April 2004 (I think). The computer tells me I have 14k miles till next service. Have checked the oil and it's a little low, but no warning light yet. I plan to do an oil change before the next service, myself, using Comma Longlife F/Synth 0W/30 (VW506 01, 506 00 and 503 00 compliant). Is this oil OK, and anything I should know about audi or diesel specific oil change procedures? Also, is there any point in doing the filter too? Thanks.