Question: what is the difference between a block heater and an oil pan heater?
Answer: A block heater keeps the coolant from freezing, and makes gas vaporize faster so the engine doesn't run as rich as long before going into closed loop. A circulating heater does the same, but also gives you cabin heat sooner. A pan heater keeps the oil from gelling, so you can run thicker oil in a worn-out engine.