The only oil you need to really worry about is the bit dried up inside the moving parts - in other words - worry about the dried up gunk you CAN'T see. Tri-flow is supposed to be safe - I try to keep it off my hands though. The regular machine oil has paraffin in it and it does set up. 3-in-1 oil sets up like concrete. When you do use the chemicals mask up etc then drink a LOT of water and flush your system. I would much rather see too much oil than rust of any kind. I would suppose you could get too much solvent in those moving areas and encapsulate solvent. I would only do that much cleaning on a really bad machine - most machines will just take a gentle cleaning. We are not talking about the average machine - we are talking about some really nasty messes. I give up on a machine that is rusted out. I know Joe and others here fix them up anyway. I have to be pretty careful with the chemicals with the chemical exposure I've already had. To keep from building up oil, just clean often and wipe up excess as you go.