When filing your hot water botle, do not use oiling water. Once the water has boiled allow it to stand for a couple of minutes before filing your bottle.
Filling a botttle with boiling water can cause splash back, which may cause burns.
Only ever fill your bottle to a Maximum two thirds capacity.
Always expel air from the bottle by lowering it carefully onto a flat surface, holding the bottle by the neck in an upright position and fill slowly to avoid water splashing back until the water appears at the opening.
Screw the stopper sufficiently tight to ensure there is no leakage. Finger tight should be adequate.