Fuel grade in A6 4.2

[David Giannandrea]

ALWAYS use premium.

You will lose mileage which will actually cost more $/mile.

You will lose performance.

Your spark plugs will foul.

My experience: I've seen both my 97 A8 and friends 99 A8 throw engine codes
when not running premium. It's not immediate, but soon enough. My friend
bought his pristine 99 A8 real cheap because the previous owner kept having
to go to the dealer with engine diagnostics. After buying the car, we
switched to premium and that was that. No more problems. Not to mention the
false economy of lost mpg. Double this experience with another friends
Jetta. He switched to premium, Jetta ran better, ran farther.

David G