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A Complete Guide To Engine Block Heaters

August 23, 2022  -  Engines & Components

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An engine block heater helps extend engine life by warming up the coolant before the engine is started which prevents dry and hard starting from oil that is thicker in colder temperatures and climates. But how do block heaters work and do you need to use one? Below are answers to common questions about engine block heaters:

engine block heater

What Do Engine Block Heaters Do?

An engine block heater works by heating up the coolant with a connection to a power source such as an outlet in a garage or shop. The block heater typically replaces an engine freeze plug, installed in a block hole where coolant is. Heating the engine coolant helps the metal components in the engine to slightly expand and the oil to become thinner in viscosity. The result is an easier starting engine. You will also have warmer air from the defroster and heater after you start the engine, as the coolant will be closer to operating temperature from the use of a block heater. 

When To Plug In Diesel Block Heaters

There is not a hard-fast rule on when to plug in block heaters for diesel engines. However, diesel block heaters are mostly used when temperatures are at or below freezing (32 F / 0 C). Some diesel owners will also make a determination based on how the engine sounds when it starts, with slower starting or more vibration from the engine prompting automotive block heaters to be used with the correlating temperature. 

Are Engine Block Heaters Worth It?

Block heaters for cars, trucks, or SUVs have value if the vehicle is in a colder climate, typically below freezing temperatures. Block heaters lengthen engine life by preventing harder starts, thicker oil viscosity when cold (which can lead to dry starts), as well as reduce friction caused by contracting metal engine parts from cold conditions. Block heaters for gas engines as well as diesel engines also make it worthwhile for the driver and passengers as the coolant is warmer and closer to operating temperature in the heating system, providing warmer air more quickly after engine start up. 

How Hot Do Engine Block Heaters Get?

Engine block heaters typically warm the engine to between 120-140 degrees Fahrenheit, depending on the model, with some providing heat below and above those temperatures. 

engine block heating element closeup
Close-up of the heating element, which submerges into the coolant
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