Define quality. Just because it is called "premium" does not make it premium.

It is simply the resistance to detonation. High boost, high compression, and high temperatures require more resistance to detonation (see, race fuel.)

 

^ That. Basically, "premium" fuel burns more efficiently in high boost or high compression engines. 2.8 V6 engines weren't designed for performance so why run premium? You don't NEED to but it is what the engine is designed for. Long story short: it doesn't matter what the rest of us thing, it's your car, run whatever the **** you want. I ran regular for 3 years and my engine never had a single problem, I also regularly clocked 33 MPG on the highway.

 

Some people are so damn ridiculous...

There is NO permanent damage done by running regular AT ALL. If your knock sensors are gone then it'll ruin it, but I'm assuming you have normal working sensors.

All that running regular does is retard the timing if you push it hard. My family has ran almost every type of german car ever on regular. It makes them slightly less powerful at open throttle but the mileage does not significantly suffer.

Heres some personal proof:
-Moms A4 2.8 went to 220k miles, NEVER saw premium after 50k.
-Dads C230 Kompressor (supercharged) gets 40+mpg on regular
-Moms new car a S430, runs great with tons of low torque on regular
-GET THIS, my Dads PORSCHE runs fine on regular (he puts 93 in when he races it)
-Friends A4 2.8 runs perfect on regular too

 

When I 1st got my a6 2.8 I ran it on87 thinking I was saving about 15 bucks every full up. After the 4th-5th fill up of gas I did the math. 30 cents of difference bw reg and premium. I usually do full tanks and that's about 13-14 gallons .3*14= 4.2 dollars. Hell if 4.2 dollars a fill up is what it takes to to even potentially avoid any problem I'll do it. I even thought about getting a corolla as a daily driver that averages 30 mpg on regular and compared to my 18mpg I once again did the math and it came out to be About 70 dollars difference a month which I personably don't think is worth buying a 5k worth car over. Again before. Did the math I thought I'd save at least 50 dollars a week but it needed up being saving just 70 dollars a month with 1000 mile commute a month.