This depends on the heat capacities of the water and oil, but nearly all oils (including Therminol1) have lower heat capacities than water so the oil would heat up faster. This assumes you have the same amounts of both materials and that both materials remain in the liquid phase (pressure is high enough to keep them from vaporizing).

If the heat capacity and heating rates are constant, then the temperature as a function of time is

T(t) = Q/(cp mass) t + T0

where T0 is the temperature at time 0. As you can see, the temperature rises faster for the substance with the lowest heat capacity if Q and mass are equal.

Dear Larry L. Baxter

Thank You so much.

Yes. Thermal oil usually has a lower Cp.

Dear Salvatore Vasta

Ok, Thank You so much.