Did you mean 1/2 cup of olive oil or 1 cup? The Liver Flush protocol is 1/2 cup of olive oil and 1/2 cup of grape fruit juice. Also oil by itself will stay in your stomach for a long time. Grapefruit juice or any citrus juice is very necessary to make the concoction sour, only sour chyme opens the duodenum sphincter. HCL does that when we have food in our stomach.
I agree cleaning intestines, kidneys, liver all are helpful before a fast. I do vitamin C flush to clean my colon/intestines, never did salt flush, I have also tried castor oil to clean my intestines before a fast.