Machtuk says,
Piston engine fuel itself is also an aid to lubrication/cooling,
Where did you get that idea? Just for starters if it's such a good lubricant why do bores wear if you run far too rich or in a car with the choke on.
As to the current problem wouldn't it be a good idea to look at what has changed in the last 18 months and what hasn't changed. If the same pilots are flying the same choppers in the same way they have been flying them for years it's hardly likely to be an operational problem. Has the fuel changed? Is it only effecting engines overhauled in the last couple of years? Is it effecting engines across the board? If it's only effecting new and fairly recently overhauled engines then maybe the cylinder manufacturers are playing silly buggers and experimenting with new ideas all the while using their customers toe beta test their ideas.
AXA says:
Ahhh, so you agree that lead affects the combustion of the fuel charge beyond merely delaying ignition then
Yes of course. It delays the onset of detonation. What should be taken from this is that changing fuels should not be taken lightly and timing varies with different fuels. When you chop and change fuel in a modern car it doesn't matter because they have knock detectors and the cars computer takes care of the problem.I don't personally know of any aircraft engine with a knock detector but there may be some.