I found that in decades of flying RR powered 75s the most pungent moments were shortly after take off and shortly after TOD, consistent with differential pressure changes in the engines.
Topping up oil levels to a less than full level did appear to reduce, but not eliminate the smells. The smell I refer to is the oft quoted "smelly socks".
I think that Airbus may yet come to regret not following the 787 example in that the 380 and 350 still get their bleed air in the "old fashioned" way.
I recently travelled on a 787 and literally found it to be a breath of fresh air.