My experience, from the mid 1970's, when I started boroscope inspections of JT8D engines, the issue was sulphidisation, the Operator was in the Arabian Gulf where the fuels uplifted had a higher sulphur content and lower lubricosity also causing premature failures in their RB211 fuel contol units. For the JT8D regular water wash was introduced. By chance they also leased ANA L1011's and had serious trouble with their RB211 engines. For the FCU's modified bearing materials helped; as these 787 seem to mostly operate within Japan local fuel might be a contributing factor.