Thanks for all the interesting answers. My gut reaction is that this concept wouldn't work easily. It's not clear to me if it's possible to readily transfer charge to the bulk of the oil, or if the charge would spread to the outside of the oil column too quickly to be carried to the top. The resistivity of the oil might also be a problem.

Having said that, I would still like to build an electrostatic machine which uses a fluid to convey the charge. It would be novel. If anyone has further thoughts or experience, please let me know.

Just now I had the idea of using particles conveyed by a gas. Powder fire extinguisher style. I need to think that one through. Metal particles would be like sandblasting and would probably destroy the machine, but some other powder might work.

Chris