My polished Russian 91% from VaporDNA was absolutely COVERED in machining oil.
Not only was it greasy to the touch, you could smell it.
Stripped down completely, and cleaned/soaked in Blue Dawn liquid dish detergent cleaned it right up.
FYI, Blue Dawn liquid dish detergent is what the clean up oil spills with.
If it's safe for the birds and such...it's safe for a liquid vapor device!
On the other hand, my KFL+ second batch(all three of them) were spotlessly clean.
I cleaned them anyway though...just to be safe.
As always, YRMV.