Diesels have a harder time starting in the winter especially when it hits the teens. Besides that with how efficient they are they don’t put out much heat, which takes them awhile to get to temp. This frost heater is a plug in unit that is installed between a coolant line that warms the coolant over a 2-3 hour period. This is set on a timer to start up before I go to work or plan to go out.. and the results are amazing. Basically in the coldest of winter my tdi will start like it’s a summers day. With instant heat! This has several benifits, including taking some stress off the starter, battery and other components. Highly recommended if you live anywhere that is cold.