So I own a 2002 Audi A4 3.0 and I was refueling today, but I wasn't really paying attention to what I was doing and put 87 fuel into my car, which recommends 91-95. Now I looked around a bit and I can't really get a definitive answer as to whether or not this will damage my engine, as people are saying the "knock sensor" should detect the different timing and retard the engine and you should be relatively okay for the tankful as long as you don't push it, and others are saying there is a good chance it damage the pistons and cylinders. Can someone please explain if I should be okay for the tank? Any help is appreciated.

 

Once time shouldn't be a big deal... don't stress it.

 

You're fine. The ECM will adjust ignition timing to prevent any damage. As Bradtyler mentioned, just don't push it until you fill up again.