In all of my previous cycles, I had used PIO in Sesame Oil. On my last cycle (that produced our daughter), I switched to PIO in Ethyl Oleate as it was the only one now covered by my insurance. I had a successful pregnancy! The only difference that I noticed is that in all of my prior cycles, I really never had lumps or anything. With the Ethyl Oleate, I developed hard, knotty lumps on both hips. Even though I haven't used it now since last August, I still have some lumps on both sides though they are much smaller than they once were. I think it will eventually go away over time, I hope. Never had that with the Sesame Oil. Bottom line though, I had a healthy baby girl so I think either will be just as effective. Good luck to you!