My understanding is that the ingredient that is the major suspect is tricreysl Phosphate.
I also believe the problem came to a head with the Bae146 which was powered by Four ALF502 engines.
John Warner selected the ALF502 because there was nothing around that could give the required performance with just Two engines.
Now the ALF502 started life as a Lycoming T55 Engine designed for the Chinook helicopter. They shoved a bloody great fan on its front end and pronounced it a turbofan. The trouble was that the front bearing arrangement for the new turbofan vibrated and also leaked oil - that went into the bleed air in quantity - or at least that is what I remember. Correct me if I'm wrong.