From my experience Castor Oil has a laxative effect of it's own (boy does it ever) Olive-Oil doesn't, you need the ES or other laxative to flush.
Also After a Liver Flush using Olive-Oil I never see any oil in the pan, wheras I see plenty of oily residue after a Castor Oil flush.
I am a great fan of Castor Oil as it has helped me lose stubborn weight each flush (2-3lbs) and the weight hasn't come back like it has on each of the 6 Olive-Oil flushes I have done.
The CO weight loss can't be down to just clearing the bowel of any residue as I would have had the same result with the OO. If anyone knows why the Castor Oil has this effect I would love to know.