Spencer
sorry it took so long to get back, had to work today and when i got home i had to
take a time out and let the back/hips/leg pain subside
anyway, as to your white powder residue, it may well be ash, and it may well have originated in the cylinder, i am not sure.
i have seen that stuff formed in many diesel engines out in the exhaust tract, engines that go on to run for many 10's of thousands of miles, and when the engine is taken down for repair, the cylinders are rarely ever found to be worn out, or have even a ring ridge.
i can only speculate as to what might be the mechanism behind the phenomena
it might be that the engine's i have seen with this white power residue all have induction hardened liners, high silicon content aluminum pistons, stainless keystone rings and turbo chargers with very large cam overlaps that send huge amounts of air during crossover out the exhaust. under such conditions it might be that the black carbon is heated to such a point, fed with sufficient air from overlap to actually burn secondarily in the exhaust manifold and form the white ash outside the cylinder itself.
there is so many factors that might have minimal, moderate, or significant effect on the formation of the white ash, where it is formed, and how an engine might tolerate the effects of the ash.
i am not sure we are ever going to determine what the root cause(s) are, much less what can be done about them unless we know what they are.
so far we have two examples of lister style engine's having worn out with the use of waste motor oil in about 1700 hours, and one listeroid (rbodell) that has a similar amount of run time but no apparent problems, a changfa that seems to be doing well at 5k hours and counting and maybe a few others that haven't reported yet.
i agree this is something we ought to be concerned about, and certainly something we should investigate further to see what we might find as the root cause, secondary causes and what if anything might mitigate the problem.
at this point it would appear that maybe treatment and filtering the oil, diluting it with diesel/rug/kerosene might have a significant effect on the outcome as rbodell has related to us.
jury is still out on this one, and it might be for sometime to come.
bob g