PLM.
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Some 757s hav been over oiled for years, 19/20 on EICAS means full or more like overfull, 17/18 on EICAS is about right.
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Some airlines like that Eng Oil is full on the first flight of the day, which often means oil is topped up during a n/stop, but oil is often topped up outside time limits which means to much oil in engine...esp nbr one or lelt....
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Any operator that has filled the air ducts with oil will need to remove said oil, two methods can be applied, clean it or breath it, cleaning costs money....
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Am sure the problem will be fixed...AAIB will be right on the case.!!!!!!!