Well, Lionel's website says it will run on O-31 curves. Sometimes a loco will run on curves a few inches sharper than the manufacturer promises, sometimes not, but I would think Lionel would mention it runs on O27, so I sort of doubt it. I know my U30C runs very well on 36.
I have some 27" curves in a box and will put together a half circle see if it fits on them tonight.