I used to sware by Valvolene 2stroke racing oil
, used it up until it was as rare as rocking horse shit. All my mates used Castrol TT and I found that when we pulled them down, theirs was full of carbon build-up on the piston crown and head also the bottom end was dry. Mine had a light tann on the head and piston that could be wiped of with a rag and the bottom end had a film of oil coating everything.
When I couldn't find it anymore I switched to Castrol TTS syn, I always found that a half used bottle always smelt like Amonia, I spoke to a industrial chemist mate of mine who tested the oil for me and yes it had a hight concentration of Amonia
, I guess that accounted for the failure of several bottom ends and pitting of main bearings caused by the acid of the Amonia.
I now use MOTUL 800 @ 40:1 with BP Ultimate, havn't had any drama's to date