It's a very simple gear pump and a couple of rams.... You could put anything in there (including water

), it'll work. As long as the oils being mixed don't coagulate then it will be fine. And aren't too thick (makes the pump work too hard)...
About a year ago I was replacing the reservoir on my trim pump and when I refilled it, I accidentally put ATF in when the rams still had 10W30 in them... All I got was a nicer shade of red :facepalm:

, system still works as designed....

I'm considering flushing the whole lot out and
putting Tellus T32 in... (Google that Bondo!!! :lol