When the engine starts, it pumps oil through the engine block and other components to lubricate moving parts. When the temperature drops, the oil is thick and doesn't flow like it should. Less oil flow means more friction — and that means engine parts wear faster than they should. A block heater warms the engine coolant, which warms the engine block and the oil. It is recommended to plug in your vehicle when the temperature drops below -18 Celsius. Ideally you should leave your vehicle plugged in for four hours prior to starting the engine. Anymore than that is not required and is wasting electricity. An electrical outlet timer can help accomplish this. Plugging in your car before you start it can also lower your car's emissions and save fuel by up to 10 percent! We always recommend plugging your vehicle in during cold weather starting to help keep its vital components in the best condition possible!