Learning how to use a block heater is a rite of passage for anyone living in the northern part of the country, where winters can be harsh and temperatures regularly drop below the freezing point. You know you’re in a cold part of the world when you see little plugs dangling from the grilles of every car you encounter on the street. Have you ever wondered what those things are? Or exactly how a block heater works? It’s an interesting, yet simple device that has probably saved more engines and gotten more people to work on time than any other winter-specific automotive add-on.
The Key Is Coolant
Although the term “block heater” is most common when referring to these winter warming devices, in reality most designs feature a “freeze plug” installed in place of your engine’s expansion plug. This serves to actually heat up the coolant that flows through your motor. Even though antifreeze isn’t circulating when the engine is off, the heat from the plug transfers throughout the cooling system via this fluid and slowly creates a blanket of warmth throughout the engine block. In turn, this also keeps the engine’s oil temperature from plummeting to the point of a solid, sticky mess.
Easier Starting, Warmer Cabin
Why is it so important to keep oil and coolant warm in the dead of winter? When being instructed on how to use a block heater, you’ll often hear how thick, cold oil can’t adequately lubricate the inside of your engine. This issue can lead to damage and excessive wear during a cold start.
A block heater keeps the motor just warm enough that oil is able to flow properly, which also eliminates resistance from the pistons while they are being turned by the starter. A car that starts quickly is only one positive aspect of learning how to use a block heater. Your car’s climate control system uses coolant to warm up the cabin, so it gets nice and toasty that much faster if the vehicle has been plugged in.
Wondering how to use this tool most effectively in the winter months? On a modern vehicle, there’s very little need to operate the block heater for more than four hours prior to starting up in the morning. This means you can save on electrical costs by using a timer to activate the heater at just the right moment in the early hours of the morning.
You won’t need to use a block heater all the time — just when the cold weather is at its worst, typically around five degrees Fahrenheit or lower.
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Having been bitten by the car bug at a young age, I spent my formative years surrounded by Studebakers at car shows across Quebec and the northeastern United States. Over ten years of racing, restoring, and obsessing over automobiles lead me to balance science writing and automotive journalism full time. I currently contribute as an editor to several online and print automotive publications, and I also write and consult for the pharmaceutical and medical device industry.