How to Jumpstart Labor

My daughter had a friend who's baby was over due so she wanted to try a home grown remedy to get things started. Someone suggest a not so reliable but well known solution, so she went to the store to purchase what she needed, while she was there she decided to call me for some recommendations. She calls and says I found the oil but I don't know what weight to buy. I'm confused as to if she means # of ozs in a can or what, so I ask what her choices are. She tells me there are several cans that say 10W30 and 10W60. After a few seconds of more confusion I realize what she is looking at and tell her NOT Castrol Motor Oil you goofy blonde, Castor Vegetable Oil.