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Engine clogging

Engine clogging causes, consequences and solution

Increasingly cleaner vehicles

Today, the challenge for car manufacturers is to develop increasingly cleaner vehicles that emit a minimum of greenhouse gases whilst limiting fuel consumption.

This is the reason why the design of modern engines has recently evolved greatly; the new technologies aim to reduce greenhouse gas emissions, for example, by improving the combustion of fuel, or by equipping vehicles with exhaust gas treatment devices (catalytic converters, SCR system, EGR valves, ...).

However, whatever the engine, old or new generation, it will still become clogged when working. In the current economic climate, consumers tend to choose the cheapest fuels which contain less additives essential to limit or significantly eliminate engine clogging.

A clogged engine loses power, becomes less responsive, can be more difficult to start and the polluting gas emissions are more significant.  

Engine clogging is inevitable and is the cause of many breakdowns, but there are solutions…

Engine clogging - main causes:


The combustion of fuel takes place in the combustion chamber of the engine, thanks to an air/fuel combination. This phenomenon is triggered by a supply of energy (compression for diesel engine, ignition for petrol engine).

Ideally, all the molecules of the fuel are burned during this combustion, but this is not what happens in reality, as some molecules or impurities contained in the fuel are not totally burned. These residues, composed of tar, soot, and calamine, settle on the valves and on the piston heads. 

The same residues can also settle in the groove of the segments, increasing friction between the segments and the cylinders. This causes the degradation of the oily film required to ensure the tightness of the combustion chamber.

The oil is then contaminated by the combustion gases and the engine consumes more fuel. Because of this lack of tightness, the oil also enters the combustion chamber and is partially burned; the fumes resulting from this combustion are rich in soot and tar, and contribute to the clogging of the exhaust gas treatment systems. When clogged, these systems are no longer effective and all the polluting and harmful combustion gases/fumes are discharged into the atmosphere.

The engine will become clogged faster during short trips, as the optimal operating temperature of the engine is not reached, and the combustion thus generates more deposits.

Injector diameters

The diameters of the injectors are becoming smaller and smaller in order to spray the fuel in the form of extremely fine droplets. This allows the air/fuel combination to be quickly homogenised and to obtain good combustion. The impurities contained in fuels can clog and even seize these injectors, reducing the optimal spraying of the fuel, and resulting in poor quality combustion and higher fuel consumption in addition to the formation of deposits.

Carburetor engines can also get clogged as carbon deposits settle on moving parts and sprinklers, resulting in a loss of engine power and a significant increase in fuel consumption.

Fuels with additives

Fuels are increasingly composed of additives, such as biodiesels, which increase the risk of engine clogging.

Composition of fuels

The composition of fuels is increasingly controlled.
Emissions Standards impose emission levels on manufacturers:

For diesel engines:
 Norm  Euro 1  Euro 2  Euro 3  Euro 4  Euro 5  Euro 6
Nitrogen oxide (NOx)  -  -  500  250  180  80
Carbon monoxide (CO)  2 720  1 000  640  500  500  500
Hydrocarbons (HC)  -  -  -  -  -  -
 HC + NOx  970  900  560  300  230  170
 Particles (PM)  140  100  50  25  5  5

For petrol and GPL engines:

Norm Euro 1 Euro 2 Euro 3 Euro 4 Euro 5 Euro 6
Nitrogen oxide (NOx) - - 150 80 60 60
Carbon monoxide (CO) 2 720 2 200 2 200 1 000 1 000 1 000
 Hydrocarbons (HC) - - 200 100 100 100
HC + NOx - - - - 5 5
Particles (PM) - - - - 68 68

These Standards require manufacturers to both optimise their engine, whilst also using after-treatment technologies for depollution.
This means a change in the composition of fuels, for example, lead for gasoline and sulfur for diesel.

Fuels are therefore less lubricated.

Consequences of engine clogging

When clogged, these systems are no longer effective for gas treatment, the engine fails and the replacement of these depollution systems becomes inevitable.
As these after-treatment systems no longer capture gases, numerous polluting gases are released into the atmosphere.

The result is increased fuel consumption with increased gas emissions into the atmosphere, and further depletion of fossil resources.

Risk of failure (injectors seizure, valves clogging).

Hence the need to regularly use additives to avoid these problems!

Solution: Use additives in fuels

Fuel additives contain, among other things, molecules with detergent properties. The structure of these molecules gives them particular properties.
The "head" is the polar part of the molecule and the "tail" is the apolar part of the molecule. This structure allows:

The reduction of the surface tension allowing:

  • finer atomisation of fuel in the injection system (increased number of finer fuel droplets)
  • larger surface of exchange between fuel droplets and the air
  • more complete and more efficient combustion which results in a significant reduction of fuel consumption
  • more hydrocarbons and particles burned
  • associated reduction of greenhouse gas emissions (CO2 and NOx)

The formation of a monolayer on the surface of the fuel system allowing:

  • optimisation of the fuel flow
  • improved lubricating power of fuels
  • protection against corrosion
  • reduction in maintenance costs

The formation of micelles:

  • around the particles of waste and dirt (prevents their deposit as they are burned in the combustion chamber)
  • detergent action and cleaning of fuel circuits

Due to these properties, with the regular use of additives to clean the entire vehicle fuel system, the engine's original performance is maintained.  This limits the polluting emissions resulting from the natural clogging of thermal engines.

Discover our additives:
Diesel or petrol injector cleaner and  DPF cleaner

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