Lisa - what brand of olive oil are you using, and what kind of a grapefruit (fresh squeezed of course) to OO (Olive-Oil) ration are you doing?
I have found that using a very high quality oil mixed at least 1:1 with the grapefruit, if not higher for the grapefruit, shaken well, doesn't taste bad at all. After not eating anything all day I find it to actually be a treat compared to the epsom mixes.
The highest quality OO (Olive-Oil) does have one characteristic that makes it tough, the burn in the throat - which I have found is a prized quality in Italian judging of quality. But before that hits me, I find the smooth taste and low acid content of the expensive organic brands to be very tolerable.