I need to precisely measure the internal volume of an open steel fixture. I was planning to do this via displacement, but I'm wondering what the best fluid would be. Ideally it should have no surface tension so that it readily penetrates every facet of the fixture. It would also be convenient if it was non-wetting which (if I understand that term correctly) means that it would not adhere to the steel when removed.
One suggestion I heard was to use water-soluble cutting fluid. Are there any other readily-available fluids with these characteristics, or well suited to this application?