How Thermostat Is a Fuel-Saving Device


The thermostat was invented in 1934 by SERGIUS VERNET was born in the year 1899 and died in the year 1968. This device is a very essential part of our vehicle  just like every other component.

It was designed as part of engine cooling system to prevent it from overheating.  The thermostat location varies on the type of vehicle; however, most are usually found close to the radiator and the intake manifold.


The thermostat consists of wax, rod, cylinder, and valve.  In many cars, the thermostat is 2 inches (5 cm) in diameter whose job is to hold the flow of coolant to the radiator until the engine has warmed up.

The standard temperature for an engine to operate is between 194℉ (90℃) and 221℉ (105℃), any temperature below or above this will affect the engine performance.

The thermostat is of high importance as it would help your vehicle not to consume too much fuel, unfortunately, in some parts of Africa, like Nigeria, some road side mechanics  ignorantly refers it to as a device that causes overheating, so they advise their customers to remove it, so wrong!

The impact of the thermostat to reduce fuel consumption remains a mystery to many.  The thermostat which is found between  the engine and the radiator blocks  coolant  flow to the radiator until the engine has warmed up, that is the thermostat  enables the  flow of coolant into the radiator only at the right time.

The thermostat prevents engine wear, deposits and emission by enabling the engine heat up as quickly as possible.


  • The thermostat regulates and controls the circulation of coolants in an engine.
  • It prevents the vehicle engine from overheating.
  •  It also keeps the engine from being too cool.
  • The thermostat helps the engine to get warm quick after cranking.
  • It enables the engine to maintain its operating temperature between 194℉ (90℃) and 221℉ (105℃).
  • Amazing but true, it limits fuel consumption in our vehicles.
  • It controls the working temperature of an engine.
  • At  initial crank, thermostat  prevent  the coolant to flow  so as to  enable  the engine to  get to  its working temperature quick.
  • Also, it helps coolant absorbs heat before entering the radiator.
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How it operates and improves fuel economy

Apart from its common functions of regulating the engine temperature, the thermostat would help improve  fuel  economy.

Surprise?  How?  Whenever you crank your  engine, its usually at a very cold temperature, the  main  valve of the thermostat remains at a closed loop in order to prevent coolant from running through the engine ne so it can heat up to operating temperature as we see on our dashboard.

When the Electronic Control Module (ECM) or BRAINBOX senses that the temperature is heating up closer to the operating temperature, it signals the Engine Coolant Temperature (ECT) sensor to command the thermostat to be at open loop in order to allow coolant from the radiator flow through the engine for cooling.

The ECT, during this process will also command the injectors to reduce the amount of fuel sprayed into the combustion chamber. What happens with this, you will have limited amount of fuel being consumed, yet it won’t alter the performance and efficiency of your vehicle engine.

When the engine temperature  drops close to the operating range limit,  the  ECM will controls the ECT to order the thermostat to close it’s valve to stop the coolant from flowing through the radiator to the engine.

If the thermostat is absent in your vehicle, it implies that there will be a continuous supply of coolant from the radiator to the engine and cause the operating temperature below its expected range.

The low in temperature will be a cause for alarm to the ELECTRONIC CONTROL MODULE which will trigger the ENGINE COOLANT TEMPERATURE (ECT) sensor to command the injector to continuously spray the fuel into the combustion chamber so as to heat up the engine , thus, causing more fuel to be burnt.

Disadvantages of not using a thermostat

As much as it has advantages when used, so likewise, there are disadvantages when not used. As earlier discussed, the popular saying being spread by  many  roadside mechanics in Nigeria  that the thermostat in cars causes engine overheating and the Nigeria weather is too harsh on car engines.

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This belief has led to the condemnation of lots of car engine. Removing the thermostat will simply make the engine over cool, which is bad.

It will increase fuel consumption, as the engine CTS (coolant temperature sensor) will assume the engine’s not up to normal operating temperature, and simply inject more fuel in. This will cause premature engine wear, as the excess fuel will wash the oil from the cylinder bores.


The overheating of Vehicle is one of the common disadvantages of not having car thermostat which can cause severe consequences.  As  earlier explained, when the  engine  temperature  gets to  its  standard  operating temperature, the thermostat  release coolant to  the  engine to control the heat.

If the thermostat is absent, it will allow continuous flow of coolant into the engine, which ultimately causes the coolant to dry up and then the car to overheat.

Heater Defect

The absent is one of the car heater does not work. The coolant will flow uncontrollable in the engine whether it is warm enough to need it or not.

If you turn the car’s heater on and the thermostat is absent,   cool air will come out from the HVAC. When you raise the heater temperature, it won’t reduce it. In other words, instead of remaining too hot  at all time, the engine  will have a problem with being too cold.

Temperature Imbalance

Absence of thermostat will lead to unusual   temperature changes when the engine is running or working.  The engine temperature will change unpredictably and the radiator coolant will not flow normally.

Poor Engine Performance

The  unavailability of  thermostat will affect your  vehicle’s engine performance because the  engine runs ideally at a  particular  temperature   between  194℉  (90℃)  to  221℉  (105℃).

While overheating of the thermostat can reduce performance, low engine temperature can also detour your vehicle’s engine performance.

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Most road side mechanics claims that the presence of thermostat is not necessary in vehicles because it causes overheating.  They claim the weather in Africa is different from those in Europe or America.

This  is  so erroneous  because the  vehicle  manufacturers  has place  it on a test run in the  hottest part of the world and they noticed  the  engine  temperature  remains the same  in  every part of the  world  provided the measures are put in place.

Therefore, the presence of thermostat is very important so as to keep the engine running at its operating expected temperature most importantly limit the consumption of fuel.

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