I have a 2006 A6 4.2L, the oil light came on at about 49k miles. I checked and it was down a quart, which I put in. Now at 53k miles, the light came on again and it was down another quart. I have no leaks so wondering what the issue may be?
I have a scheduled maintanence with Audi for next week.

 

Would be interested in hearing what the Audi Dealer says about your A6 oil consumption.

Personally I would be changing with synthetic oil every 3000 to 4000 miles. This would help prevent oil light from coming on between oil changes based on the mileage you menioned.

 

Check your oil filter and change the kind that they use. Some of them are too fine and they block the flow too early.
I had the same problem.
Did you add some kind of engine cleaner to your oil? In case you did all that was cleaned ended in your filter.