||Finding a new safe and ecologically friendly borehole fluid is one of the most pressing problems for forthcoming ice-drilling projects. Not all recent borehole fluids qualify as intelligent choices from safety, environmental and other technological standpoints. We propose the use of silicone oils as the borehole fluid. The most suitable type of silicone oils for deep ice drilling are low-molecular (or volatile) dimethyl siloxane oils (DSOs). Low-molecular DSOs are clear, water-white, tasteless, odorless, neutral liquids. They are hydrophobic and inert substances that are stable to water, air, oxygen, metals, wood, paper, plastics, etc. Of the DSOs, class 2 grades of KF96-1.5cs and KF96-2.0cs most fully fit our criteria for choice as borehole fluids. The final conclusion as to the suitability of DSOs for ice deep drilling will be made after the experiments in a test borehole.