The 4000 uses about 96mls. Not sure if the 4800 is the same.
Power Clean should not be automatic, it is a 'last resort' clean. Are you sure this is what is happening? If so, call Epson Prographics and ask if this is working as it is supposed to.
usually the printer asked before doing power clean and I say no, after it went through its process it made al lot of noise which sounded like a power clean, I had a look at the maintenance tank and there were bubbles in the top which I am thinking were fresh ink.
What do you think?