Thanks for the offer Andy. I don't have time for engines right now. When I do I'll make up a batch. I imagine the contra you mentioned as a self adjusting unit depending on spring pressure acting against chamber pressure to vary the combustion chamber volume. CVEC's muffler works on the same principle.

The used engine oil might have less active additive package and maybe doesn't have the problems some mentioned with new oil.

The veggie lube is intriguing but I want to know what the properties of the resulting lube are. When I look at existing oils a quick look at the spec sheet tell me what I want to know.