What Is an Engine Block Heater and Do You Really Need One?

Preheat your car like you preheat your oven.

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Humans use hot cocoa, coffee, tea, whiskey, and chicken noodle soup to warm up their insides and defrost from the cold abyss known as winter. Cars use engine block heaters.

For the most part, modern vehicles have been engineered to drive and function in any weather, but no matter the torture-testing regimen manufacturers employ, extremely cold temps still affect things such as fluids and batteries. Drop too low, and the car might not start, and that isn’t good for your commute.

To quell this issue, which directly affects markets like the northern United States and Canada, the engine block heater was invented. This small device heats up select parts of the powertrain to make cold starts quicker, easier, and less stressful on engine components.

Sound like something you need? The Drive’s die-hard informational team has created a guide to determining whether or not your vehicle needs an engine block heater. Let’s figure this out together.

What Is An Engine Block Heater?

An engine block heater is an electrical device designed to warm a part of the engine and/or the motor oil when the vehicle is not in use. There are numerous types of engine block heaters that use various methods to provide the heat.

What Does an Engine Block Heater Do?

The purpose of an engine block heater is to heat the engine block and its internal fluids, particularly the motor oil. Why? Because cold oil becomes more viscous, which makes it more difficult for the engine to turn over.

By using an engine block heater in a cold climate, your car will start up easier and use less energy. Additionally, because the engine will achieve its optimal running temperature sooner, the driver can put the vehicle under full load sooner without worrying about overstressing the engine.

A Ford engine block heater.
Some types of engine block heaters are designed to plug right into a car., Ford

Types of Engine Block Heaters

There isn’t just one type of engine block heater. Some engine block heaters are used on the exterior of the block while others are incorporated into the engine. Some heat the fluids, while others heat the block. To determine which type you want or need, you first need to understand how they work. Let’s untangle the wires. 

Core/Frost/Freeze Plug Heater

This type of heater replaces the existing core plug, also commonly referred to as the frost plug or freeze plug, and directly heats coolant within the engine using an element that sits in the coolant. You can use your car’s service manual to find the location of the plug.

Engine-Warming Blanket 

Placed on top of the engine or attached to the underside of the hood, an engine-warming blanket disperses heat across the engine block.

Oil Pan Heater 

An oil pan heater is essentially an automotive-grade heating pad that can be placed on the oil pan or a different part of the engine. Typically attached with magnets or bolts, the pad warms up the oil pan and the oil inside.

Dipstick Heater

A dipstick heater replaces the dipstick with a long heating element that warms up the oil.

Inline Heater (Circulating) 

Inline heaters require some work, as they are spliced into a coolant hose. Circulating models use the existing pump to spread the heated coolant throughout the system.

Inline Heater (Non-Circulating) 

Non-circulating inline heaters are also spliced into a coolant hose, but the heating is restricted to that spot.

Bolt-On External Heater

A bolt-on heater is directly attached to the exterior of the engine block and heats it from the outside in.

An oil pan heater with a plug and a heating pad.
An engine warming pad can be placed on the engine or the oil pan., ABN / Amazon

Do I Need An Engine Block Heater?

Do you live on Hoth? Are you thinking of moving beyond the Wall?  If so, maybe! Generally, if you live in a climate where you regularly experience temperatures below 10 degrees Fahrenheit, it’s not a bad idea. If you live where those temperatures are a rarity, probably not.

When Should I Plug in My Engine Block Heater and How Long Should I Use It?

It is not necessary to keep an engine block heater plugged in overnight. Once the engine reaches a certain temperature, the extra heat will be lost to the cold air, and electricity is wasted. In regions with deep freezes, it’s best to turn the engine block heater on approximately 3-4 hours before you plan to drive the vehicle. Using a timer that automatically starts the heater is useful for early morning rides.

WARNING: Do not drive away with the heater still plugged in! You’d be shocked how often this happens, especially if people haven’t had their coffee.

How Do I Use an Engine Block Heater?

Some heaters, such as the dipstick heaters, are easily installed, while others such as the inline heaters might need professional installation. Use your judgment, based on the type of heater and your DIY comfortability. Once the heater is installed, all you do is plug it into an extension cord that’s connected to a regular house plug.

An engine block heater.
Kat’s offers numerous types of engine block heaters., Kat’s / Amazon

Engine Block Heaters vs. Idle Warm-Up

Starting your car and leaving it to idle for 5-10 minutes does not replace the need for an engine block heater. An engine block heater does its work before the car is started and makes that start easier for the vehicle. Besides, with the planet on fire and all, it’s probably best not to leave your vehicle idling.

Do Modern Cars Still Need To Be Warmed Up?

If you’re trying to warm up the inside of your vehicle, then yes, but know you’re hurting the environment. If you drive a modern fuel-injected vehicle and are trying to protect your engine, then no, that’s not necessary and could potentially cause slight harm to the engine.

The Drive spoke with Jason Fenske of Engineering Explained to talk about why it’s no longer necessary to warm up your engine before driving off. “My thoughts on warming up your car’s engine have changed somewhat [since the video below],” says Fenske, “I don’t think it’s bad necessarily, but I don’t think there’s much point to it. I had a chat with a big-brand powertrain engineer who said basically ‘As long as you don’t floor it immediately, after about two seconds, you have oil flow and are good to go.’” Fenske added, “But the major point remains, in my opinion, [there’s] no need to warm it up, unless you’re doing so simply for your own comfort/to melt windshield ice/etc.”

As for block heaters, Fenske said, “Block heaters are a good idea!”

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Tony Markovich Avatar

Tony Markovich


Tony Markovich is a former Senior Editor at The Drive, departing in 2022.