Good news––I think I have finally eliminated my engine faults (knock on wood). I was able to drive 2 tankfuls without a CEL. But in the process, I measured my engine replacement at about 1L/2000km.
I have replaced a number of oil seals (most recently the oil cooler o-rings) and the car seems to be clean below, so I can only attribute the loss to oil burn. Is this amount common for a 14y old engine or excessive?
At 187k miles, I burn about 1-1 1/2 qts every month/1400 miles.
I burn about that amount on my '14 q7 3.0t, about a quart every 2 or 3k, has about 130k miles.
My s6 5.2 has a newer motor ,70k miles and doesnt burn any oil 
Our 4.2 a6 burns about 1L for every 3k miles. It has about 145k on it.
Topped off before our autumn trip to Sweden.
2200 km and the oil level is almost the same as when we took off.
Same outdoor temperature and same parking spot between the measurements.