Learning how to use a block heater is a rite of passage in Canada. You know you’re in a cold part of the world when you see little plugs dangling from the grilles of every car on the street. Have you ever wondered what those things are? Or exactly how a block heater works? It’s a deceptively simple device that has probably saved more engines—and gotten more people to work on time—than any other winter-specific automotive add-on. And if you think modern engines no longer require this accessory, you may change your mind after you’ve experienced a very cold start at minus thirty.
- Difficulty: Easy
- Duration: 10-30 minutes
- How often: As needed
Coolant Is Key
The term block heater is commonly used to refer to these winter warming devices. In reality, most designs feature a freeze plug installed in place of your engine’s expansion plug that serves to heat up the coolant that flows through your motor. Even though antifreeze isn’t circulating when the engine is off, the coolant carries the heat from the plug through the cooling system and slowly warms the entire engine block. This also keeps the engine’s oil at a good temperature and prevents it from becoming a solid, sticky mess. Note that you can also find magnetic heaters that can simply be attached to the engine block.
Easier Starting, Warmer Cabin
Why is it so important to keep your vehicle’s oil and coolant warm in the dead of winter? When learning how to use a block heater, you’ll often hear that thick, cold oil can’t adequately lubricate the inside of your engine and can lead to damage and excessive wear during cold starts.
A block heater keeps the motor just warm enough for the oil to flow properly, thereby eliminating resistance from the pistons when they’re turned by the starter. But a block heater doesn’t only ensure quick starts. Since your car’s climate control system uses coolant to warm up the cabin, it will get nice and toasty that much faster if your vehicle has been plugged in.
When to Plug In?
Wondering how to use this tool effectively in the winter months? On a modern vehicle, you generally don’t need to operate the block heater for more than four hours prior to starting up. This means you can save on electrical costs by using a timer to activate the heater at just the right moment, in the wee hours of the morning.
You won’t need to use a block heater all the time. Only plug it in when the cold weather is at its worst, typically when the temperature drops to minus fifteen or lower. The extra watts you spend will be recovered with a better gas mileage, since your engine will be quicker to reach its optimal temperature. Needless to say, your motor will appreciate the extra help when you start it on a minus‑thirty‑degree morning.