Oscar II England Departures

I just found this site, so hope that I am not asking a question that might have been answered before. My mother came to New York in 1920 and told me that she had traveled on the Oscar II from England. I cannot find any departure on this site which indicated that the Oscar II departed from England in that year. Can anyone guide me to such departures, or is it possible that my mother was incorrect in the ship name? Many thanks for any and all information and assistance. Charlie