can you please tell me, how do we measures the conductivity and dielectric constant of silicone oil and castor oil, because resistivity of silicone oil is very high so thats why it is difficult to mesure with conductivity meter,
Sorry, but your question is so vague and general that it is impossible to give a reasonably accurate answer, especially not knowing in what context you are asking.
Because both of these substances are dielectrics, you will have zero conduction below the breakdown voltage for the insulator. Measurements of resistivity can only be made in the material if current is flowing, so you would have to use a high power resistance meter to measure conductivity above the breakdown voltage. as long as you are below the permittivity voltage, current should not flow.