If you're traveling from SFO and are Star Gold or traveling in C or F on any Star carrier (other than SQ), you can no longer use the SQ lounge -- you have to use the UA RCC. Was advised this by the SQ lounge agent -- it became effective in mid-Jan, commensurate with the launch of SQ's new J and F class products to ICN/SIN.

To clarify, I don't actually know if the SQ lounge will turn away a Star Gold pax traveling in Y on the SQ flights. The agent simply said that the lounge is no longer a Star Gold lounge. I was traveling on UA in C.