I myself wanted to use motor oil for wood finish (on some outdoor pieces),
but never got to actually doing that...

Not good at all for your backside. As a young man we used diesel fuel
for form break treatment when we were pouring lots of concrete.

Then we used motor oil thinned with gas if we ran out of that.

It was the only time we really needed to wear gloves as we got a red,
irritated burn on our hands from working with the forms after
treatment.

Robert