"Turbo diesels don't like having the oil at max. as more gets drawn into the turbo. Handbook says to keep it at middle between the marks
In the Audi Service book it divides the dipstick into A, B, and C
"When the engine is working hard......the oil should preferably be kept in Area A (but not above)
Area B - "it is sufficent if the oil level is somewhere in this area.
Area C - "oil must be topped up"
Maybe, if you are talking from experience, the pd unit prefers to have the oil inbetween the min and the max.
i can see why it would be harmful to go over the max, but i think i will keep my oil in the A area......mind you it always uses some and will go down to Area B........then i will top up. 160k miles and still going strong.