I expected a slight performance increase from running 98RON (US:93) over the standard 95RON (US:91).
Instead it was like the engine didn't like using it at all. It's gone back to normal since I switched back to 95RON (US:91).

^{_D.D._[an Englishman living near Ingolstadt, Germany]_}
My Car History | My A6 0-155mph/Autobahn on Youtube

My 2004 2.7T Avant. It's days are numbered, don't have room for two cars.