Use the water temperature specified in the disposer instructions; cold running water is the normal requirement during grinding. A motor that turns without water is not evidence that dry operation is suitable.
What the observation tells you
Water helps carry the processed waste through the outlet. Using hot water to make greasy scraps disappear changes their appearance without removing the grease from the drainage system. Keep fats and oils out of the disposer altogether.
A useful next step
Establish the correct flow before feeding suitable food. If the cold supply is unavailable, collect the scraps separately until it returns rather than improvising a dry grinding session.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.