Irony is oil is not good for rubber, I don’t know how much oil can go back into rubber anyway.
someone told me simple green will soften a tire. There is nothing I see on the MSDS that would suggest that, but then I don’t know much at all on the chemistry.
A lot of suggestions for wintergreen oil.
My personal feeling is that I wouldn’t waste the time on it. I don’t do voodoo and tire prep seems like voodoo. Just a lot of effort dirt trackers go through. A lot of testing to see what works and only good for short term, Not worth it for the odd old set. You might be better getting a set of current take-offs.
Here is an article the might help you decide.
I would look at some MSDS on what is supposed to work. Or just don’t mess with it from a safety and consistency standpoint.