Help with air filter regulator - minimum oil level??

[TP21]

Hi - Newbie to filtering my air from my compressor.... I have something that looks like this:

https://www.toolstation.com/shop/p2...b6haTQaPnvtpxlNpTooXH0iwqY_18JwoaAo2WEALw_wcB

But don't have any instructions...

There are two markers on the side (maximum drain level) which I presume is the maximum amount of water it should hold before draining? But it also has 'minimum oil level' - do I need to add oil to this? If so what type of oil?

Many thanks!

 

[rtbcomp]

I suspect the same label is used for oiler and filters, I've never put oil in a filter!

You're right about the 1st mark, maximum water level.