I dipped the in a stick to look at the old oil, it looked pretty clean like new. Draining it is fine, but if I can remember which of these I put in the past, I can just add more now and be done with it.... hate things like this happen in the middle of the project.
Is there such a 2-cycle or 4-cycle for this pump's fluid/oil? I guess not?
The reason I asked because reading back on old replies, but I guess it is for gas motor, which I don't have. My motor is electric. Am I right?
Thanks guys.
..... I can't remember what did I use the 2-cycle engine oil (in the pic above) for if not this air compressor's pump. I think I will add it in tonight, temporarily for now and will drain out after couple weeks. If anyone can see that it will destroy my compressor, please stop me

Thanks again.
BTW, what "makes 2.5 gallons" means? Do they use this oil to mix with something else? I know that I didn't, because I never mix any oil/fluid in the past.
I wish I have good memory....