Water at 100 degrees and oil at 100 degrees are both 100 degrees, but they have different specific heat capacities, and water has a larger specific heat capacity.
One kilogram of water releases about 4,200 joules of heat when the temperature is lowered by 1 degree, whereas oil releases only 2,000 joules of heat, so 100 degrees of water is much 'hotter' than 100 degrees of oil.