I have a 2015 A6 3.0T Quattro that I use 87 octane in even thought the fuel cap says 93 only. This is not the first Audi that I have had and each one says 93 octane on the fuel door. But if you look in the owner's manual it states that the car can use 87 octane at a reduced performance. The car runs fine on 87 octane and has plenty of power. So I don't know what performance is reduced.