I used it with my second child it worked for me labor,lasted maybe 3 hours no pushes and my daughter was born healthy
Its a laxative... And back in the day people would use it when they were overdue to jump start labor...
The motor oil you're thinking of is Castro... I think.
It's more or less a laxative, and it's claim is that it stimulates contractions which bring on labour. More often though it just causes the female to be extremely uncomfortable and remain pregnant.