Can you explain the miracle where Sai Baba lit lamps without oil?

Sai Baba had a great love for lighting lamps in the mosque and temple. He would go to local shopkeepers daily to ask for oil. According to Chapter 5, the grocers grew tired of this and conspired to refuse him. When they all said no, Baba returned to the mosque, took his tin pot which had a tiny bit of oil, poured water into it, and drank it as an offering. He then filled the lamps with plain water, soaked the wicks, and lit them. Miraculously, the lamps burned all night using only water, which amazed the grocers and made them realize their mistake.