Two years ago I was advised by a local Bosch service owner (he's around 70) to pour "half a litre of 2-stroke oil" into each tank of my 2,0 HDi common rail Peugeot when taking some old Deutz injectors for overhaul. "Once you'll have to refurbish the common rail injectors, it won't be that cheap," he added.
Walkabout: the other forum suggests the 1:200 ratio. Yes, it's mainly for lubrication purposes since new eurodiesel fuel is dryer and thus looks like failing to lubricate the pump and the injectors as it should. If you only read the first 4 pages of that thread you'll get a quite reasonable insight into it.
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