everyone ive always asked about it has always just laughed and said "dont worry about it, they all do that" but ive always thought they shouldnt,theres no real reason for a good health engine to do that. mine still did it a little on over run even after spending £2000 having the rings done,a new recon head fitted and another £700 on a brand new turbo and still being told to expect to use about a litre of oil every thousand miles or so just because cosworths do.