Sure, the light and mist function works separately, you can turn off the light by long pressing the LIGHT button about 2 seconds.

With full 200 ml water, strong mist can last 6-8 hours.

Yes, the oils are optional, you can use it without oils. lt just like a humidifier without the oils

The noise level of this diffuser is only 23 dB, the ulra-quiet fan can effectively reduce noise. it won't disturb you at night