i certainly wouldnt be putting oil inside a mod on a centrefire you will end up with a big bang!!
i'm no gun expert but,
it was advice given to me by someone who has had guns along time, and i dont plaster it in heavy oil, just spray it out with WD40,
and been doing it since i've had it,which has gotta be around 8 years now, and had no problems, so cant be a bad thing, but your entitle to your opinion,
cheers,
jay,
WD 40 is what is recommended by manufacturer.
cheers mate,
jay.