Interesting summation from one, in the Reader Comments from Rope's link above:
Rolls Royce engines have more oil fume issues than GE or Pratt engines.
RB211-535C has oil fumes issues with 757s
RB211-535E4 as well.
BA has always had this problem on the 757,767 fleet for years.
The 524Gs on the 767 ( and 747) have oil fume issues as well.