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  • An engine block heater is a device that heats the engine block while the vehicle isn’t running.
  • The engine block heater can warm the block, motor oil, and coolant to make starting your car easier.
  • Engine block heaters come in different types, like core plug heaters, dipstick heaters, and engine-warming blankets.
  • Avoid leaving the engine block heater running all night.Instead, use a timer to start it at the right time.
  • Heating the engine with a block heater isn’t the same as warming up the engine.

Sometimes, it can get so cold that you can’t leave home until you get a cup of your favorite hot beverage in your belly. Similarly, your car might struggle to start and operate at very low temperatures. You must wait for the engine and various fluids to sufficiently warm up before it becomes safe to drive your vehicle.

Much like how you warm yourself up with hot chocolate or coffee, your car can use an engine block heater to warm up faster in cold temperatures. Also called a block heater, it can prove indispensable if you live somewhere that gets really cold during the winter.

What is an Engine Block Heater?

Engine block heaters are devices that increase the temperature of the engine block when the vehicle isn’t running. Also called block heaters, they have an externally powered heating element that connects to an engine part, such as the oil pan.

red car with an attached engine block heater
Engine block heaters are devices that increase the temperature of the engine block directly or indirectly by heating engine oil, engine coolant, or both.

What Does an Engine Block Heater Do?

Depending on its type, the engine block heater can warm the block directly or indirectly by heating engine oil, engine coolant, or both.

Using an engine block heater becomes critical during winter when temperatures can drop to zero or lower. Oil becomes more viscous than usual in cold temperatures, and this slows down the moving parts coated with it.

When you start a car with cold engine oil, turning it over might take more effort. The prolonged start-up sequence will also consume more fuel and generate more emissions.

You can alleviate this problem with an engine block heater. Heating the engine block will warm the motor oil, reducing its viscosity and making starting the car easier. You can also put the engine under full load sooner. Pre-heating lets you save time, effort, and fuel.

Engine Block Heater Types

There are many types of engine block heaters in the market. While they do the same job of heating the engine, they differ in terms of where they connect to the engine, how they raise temperatures, the part that gets heated, and whether the heater is external or integral to the engine.

The most common and popular engine block heater types are the following:

Bolt-On External Heater

Some engine block heaters are mounted outside the engine. They bolt onto the exterior of the block and warm the entire set-up from the outside.

Core Plug Heaters

A core plug heater directly heats the coolant fluid in the engine with the help of a heating element. The core plug heater goes inside one of the sand-casting core holes, which are holes formed when the engine block is cast and appear in certain parts of the engine. Covering the core holes are core plugs, which prevent coolant from leaving the passages.

Using a core plug heater requires removing one of the core plugs from a core hole. Refer to your car’s service manual to locate the plug.

Alternative names for the core plug heater are the frost plug and freeze plug heater.

Dipstick Heaters

This type of heater resembles the dipstick, the tool you use to measure engine oil levels. Like its namesake, it fits inside the dipstick tube leading to the oil reservoir.

To heat the engine with the dipstick heater, start by unscrewing the oil reservoir cap. Insert the heater into the tube.

Engine-Warming Blankets

An engine-warming blanket features thermally conductive material with electric wires running through it. When you plug it into an electrical outlet, it grows hotter and radiates heat that can warm the engine.

Some engine-warning blankets spread over the top of the engine, while others fasten under the hood. No matter the design, the engine blanket spreads heat across the engine block.

Inline Heaters

Inline heaters intertwine with one of the coolant hoses. They raise the temperature of the engine coolant, melting any fluid that has frozen up and warming the liquid until it can flow through the engine again.

There are two types of inline heaters. The circulating type uses the coolant pump to move the heated fluid throughout the cooling system and the engine. By spreading the heat this way, the heater can warm up the engine faster.

On the other hand, non-circulating inline heaters only heat the coolant in the hose. They don’t spread heated coolant like their circulating counterparts.

Oil Pan Heaters

The oil pan heater is a heating pad that warms up the oil pan and the motor oil in it. You usually set it on the oil pan, although some designs require placing them elsewhere on the engine. An oil pan heater may use bolts or magnets to fasten itself to the pan or engine block.

How to Use an Engine Block Heater

The exact process of using an engine block heater varies according to its type. Compare the dipstick heater and the engine-warming blanket. You use the former heater by inserting it into the dipstick tube while you spread the blanket over the engine or fasten it to the underside of the hood. If you’re unsure how to use an engine block heater, consult its user manual.

Avoid leaving the engine block heater running all night. You only need to get the engine and motor oil to a specific temperature. Past that temperature, any additional heat will only waste electricity.

If you live in an area that experiences deep freezing temperatures, turn the engine block heater on three to four hours ahead of the time you plan to drive. There are timers that you can set to activate the heater at the right time.

Differences Between Using an Engine Block Heater and Warming Up the Engine

At first glance, heating the engine block might sound the same as warming up the engine. However, these are different processes.

You can tell them apart by looking at the following factors:

Time of Use

An engine block heater is used several hours before starting the vehicle. It makes the start-up sequence much easier during cold days.

In comparison, warming up your car takes place after you start its engine and requires a successful start-up sequence.


Most engine block heaters run on electricity. Plug the heater into the appropriate outlet. If the power cord fails to reach the outlet, bridge the gap with an extension cord. The device doesn’t burn fuel or drain the car battery.

As for warming up your car’s engine, you must start and let it run idle for several minutes. Running the engine consumes fuel.

New Vehicles

Modern vehicles can benefit from pre-heating their engines with a block heater. After all, the computers that control various helpful processes are usually offline when you use an engine block heater.

However, warming the engine up isn’t necessary in cars with modern powertrains. The powertrain control module (PCM) will automatically adjust the engine’s performance during a cold start to ensure it quickly reaches the optimal operating temperature.

About The Author
Written By Automotive and Tech Writers

The Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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