Replacing old wires stuck on pipes inside concrete walls with new Cat6 cable
No, don't use oil for this.  It's flammable and also acts as a solvent on my materials.  There are commercial &quot;wire lube&quot; products that are safe for lubricating wires.  Most big-box home centers and all electrical supply houses have a selection of these.
But the trick is going to be getting the lube to where the restriction is assuming that the wire itself is not clamped, tied, or tangled on something that lube will not fix.