Why do microwaves heat oil faster than water?

It is generally believed that oil does not absorb microwave energy due to the small dielectric loss factor (only 1/100 that of water). Here, we compared the heating rates of four cooking oils versus water in a microwave oven under the same experimental conditions. Contrary to general belief, we found that oils heated 1.4 ~ 2.0 times faster than water in microwaves. We developed a theoretical explanation to show that a 10-fold stronger electric field was created in oil compared to water, resulting in approximately equal amounts of microwave power being absorbed by oil and water. After microwave energy had been absorbed, oil heated faster due to a smaller specific heat value (1/2 that of water). This study creates opportunities for electrifying industrial heating of oils and oil-rich biomass with microwaves, which would move the processes toward carbon-neutral operations.