I think the most critical aspect of proper lubrication in the FD has been neglected in this discussion. Have you all forgotten that the major component failure of the FD is the turbo(s). Specifically, bearing failure caused by the by-product of burned oil (coking)as result of over heated turbos.

Synthetic oils are ideal for turbo charged engines with oil cooled turbos because they don't burn at the temperatures that turbos typicaly see, especially our rotaries, were as mineral based oils do. Here lies the problem. Unless the oil that is injected into our rotaries (to keep them happy) is burned sufficiently, an accumulation of oil will develop somewhere. It's quite simple really, determine the combustion temperature of a particular synthetic and compare it to that of the combustion temperature of the rotary. A lower synthetic combustion temperature would indicate to me that there's a pretty good chance that the engine is consuming what it is ingesting.