New Diesel Toyota Corolla 1.4D4D using oil

I recently bought a brand new Diesel Toyota Corolla 1.4D4D for my wife. <br> <br> From day 1 it used oil...lots of it. After exhaustive testing, Toyota discovered that it uses around 1 litre of oil for every 3 500km driven, or roughly 4-5 litres of oil between service intervals. <br> <br> They send me an official letter refusing to do anything about it because, and I quote \The preferred specification