mobil one 10/30 full syn, changed every 5,000 or 6 mnths... whichever comes first.... either a k&n or mobil 1 oversized filter....
94 i6 5spd 225,000m, 100,000 on 97 engine, no problems...
btw, switched to syn with @ 60,000 on the 97 engine, (soon as it was installed, back in 02), never...