Turns out, at least theoretically, oil cleanser/makeup remover is 卸妆油 (Xièzhuāng yóu)
And I know this because in my Wechat Moments today appeared an apparently comprehensive list of translations for every conceivable makeup/skincare/haircare expression:
All the Makeup Words (ignore the cat):
http://mp.weixin.qq.com/s/lXBi1HnHdLcr4qtYqBblYQ