Engine Block Heaters: A Winning Tool for Winter Weather

Winter’s chill can have devastating effects on your car—particularly overnight, when your vehicle sits in sub-zero temperatures. During the coldest months, engine oil turns to slow-moving sludge, coolant threatens to ice up, and metal gets brittle. These issues can quickly wear down your motor’s internal components and potentially drain your battery as it struggles to turn over your reluctant engine.

If you live in an area where very cold temperatures are a daily fact of life, you’ve probably already struggled to combat its negative effects. Fortunately, one of the most useful winter tools for your vehicle is also one of the least expensive: an engine block heater.

How Do Block Heaters Work?

While there are many different types of block heaters, they all use electricity to keep your motor warm, providing a basic layer of defence against the cold. Most designs rely on a constant 110-volt connection to household electricity, which means that you’ll need to access your home’s current via an extension cord for effective use. Some, however, can be tagged in using an auxiliary battery system that is devoted exclusively to engine warm-up. These types of systems are typically found on commercial vehicles.

Block heater designs differ based on which parts of the engine they focus on. Most heaters warm the coolant, which then carries the heat through the water jackets in the block and provides an even level of warmth throughout most of the motor. These types of heaters are installed inside a radiator hose or in place of a freeze plug.

Another common type of block heater warms the engine oil, either externally on the oil pan or internally through the dipstick tube. There is also an electric blanket design that is laid over the top of the motor or bolted to the block itself.

Which Block Heater Works Best?

Which type of block heater is the best choice for you? The answer depends on a few different factors.

If you live in an area where cold snaps are common but not extreme—think -20 °C rather than -40 °C—a coolant heater or a bolt-on heater is probably your best bet, as they will provide enough all-around heat to facilitate engine starts in the morning. If cold weather is rare but possible, you can probably get away with covering your motor with an engine blanket on nights when you know the temperature is going to drop.

In very cold climates, an oil heater will greatly reduce the amount of time your motor’s internal assembly spends spinning before it’s properly coated and protected, as warm oil moves and coats more quickly. Combining two different types of heaters is also possible, and even recommended in areas of extreme cold.

Some block heaters, such as those that insert into the dipstick tube or attach to the oil pan, are relatively easy to install on your own. Others, including in-hose coolant heaters, are a little more challenging, while bolt-on block and pan heaters, as well as freeze plug heaters, are typically best left to a professional. If you’re buying your car new, ask if you can have a block heater installed at the dealership for a nominal fee. If you’re buying used, check to see if the car already has one, and if so, determine the type.

Check out all the engine products available on or trust one of our 600 NAPA AUTOPRO shops for your car routine maintenance and repairs. For more information on block heaters, chat with an expert at your local NAPA Auto Parts store.

Benjamin Hunting