Gasoline Additives: The Definitive Guide

Gasoline Additives with stabilizer can in reddish background

Gasoline additives make up for 10-20% share of gasoline. These additives are helpful to enhance the engine performance – leading to better combustion, fewer deposits, and better health of the engine.

Here are the typical additives added to gasoline for better performance:

  1. Anti-knocking additives
  2. Antioxidants
  3. Corrosion inhibitors
  4. Deposit control additives (detergents)
  5. Other additives like oxygenates, friction modifiers, drag reducers, dyes, etc.

Let’s dig deep into each of these gasoline additives one by one.

#1: Anti-knocking Additives

Knocking arises because of uneven combustion of the fuel inside the engine, giving way to a weird thudding noise. The air-fuel mixture in the engine does not burn smoothly leading to uneven shocks in the engine and hence, the noise.

This noise along with the entire uneven combustion is called knocking. If knocking continues, it can damage engine parts like the valves and the piston. The heat is lost as well, leading to poor engine performance.

And that’s why anti-knocking agents and additives are added to gasoline to prevent engine knocking.

The anti-knock additives reduce knocking by increasing the fuel’s octane rating.

Now, Octane rating. This is basically a measure of how much the fuel can resist heat and compression without detonating. In other words, how much the fuel can withstand heat and pressure to prevent knocking.

While the desired octane rating can vary depending on the engine design, compression ratio, and the type of fuel used, high compression gasoline engines usually require a higher octane rating for the fuel.

These anti-knocking agents reduce the engine’s knocking and increase the octane rating by raising the temperature and pressure at which auto-ignition occurs.

The lead alkyls tetraethyl lead (TEL) and tetramethyl lead (TML) are the two most widely used anti-knocking agents. However, there has been a reduction in their due to these agents containing lead.

This problem with lead usage has given rise to ash-less antiknock additives, such as N-methyl aniline (NMA), amines, N-nitrosamines, iodine, selenium compounds, etc.

#2: Antioxidants (Stabilizers)

Gasoline over time absorbs oxygen to form hydroperoxides. These hydroperoxides form free radicals and initiate a chain reaction that generates the oxidation products which ultimately form gum.

And you don’t want gum formation in gasoline. Nor do you want any free radicals or chain reactions.

Enter antioxidants.

Antioxidants are organic chemical compounds that decrease the oxidation and gum-forming tendencies of fuels.

They prevent chain reactions by donating their hydrogen atom to the peroxy radical. Thus, reducing free radicals and terminating their chain reactions.

Antioxidants provide stability to gasoline since they reduce volatility by preventing these chain reactions. Hence, they are also called Stabilizers.

Antioxidants play a vital role especially when the fuel is stored for longer periods of time.

The two most common antioxidants used today to control the gum formation in gasoline are – hindered phenols and phenylene diamine.

#3: Corrosion Inhibitors

Commercial gasoline will always have traces of water in it.

The source of contamination is many. Even as simple as moisture from the atmosphere can be picked up by gasoline.

This moisture in gasoline along with the air (oxygen to be precise) attacks the iron and other metal layers in the fuel tank and engine components to cause corrosion.

The extent of corrosion or rust formation depends on the temperature, humidity, exposure to the environment, and duration.

The rust formed can clog fuel filters and carburetor or fuel injectors and adversely affect the engine performance.

That’s why corrosion inhibitors are added to gasoline to prevent rust formation on metal surfaces.

As for how these additives work, the corrosion inhibitors prevent the adsorption of oxygen or water molecules on the metal surface.

The additive forms an adsorbed film on the metal in contact with the liquid. This film is hydrophobic and displaces the water from the metal surface. The polar end of the inhibitor molecule becomes attached to the metal surface, while the other end of the molecule is dissolved in the fuel.

One key thing to note here. These corrosion inhibitors work effectively when there are only traces of water and moisture present.

In an aqueous system, where the water content is heavy, the same corrosion inhibitors cannot be used since they are rendered ineffective by the high water content.

#4: Deposit Control Additives (Detergents)

Deposit control additives, commonly called detergents, are added to gasoline to prevent deposit formations.

Deposits in the fuel systems will adversely affect the operation of the engine. Be it motorcycles, cars, or any other machinery using gasoline or diesel engine systems. The deposits in the fuel will hinder the performance.

Take the carburetor for example. If the gasoline deposits start accumulating on the carburetor throttle and in the venturies, the air-fuel ration entering the combustion chamber is disturbed. As a result, either you will have a lean air-fuel mixture or a rich one – both leading to suboptimal fuel combustion.

The same issues occur when deposits build up on the fuel injector nozzle and intake valves. Not to mention combustion chamber deposits, which can be even worse.

That’s the reason detergents or deposit control additives are important. It shouldn’t surprise you when detergents share is about 40-50% of all the additives used in gasoline.

As for how these deposit control additives work, they have two vital components carrying different functions.

Detergent diagram with a polymer tail and polar amine

The first component, a long hydrocarbon tail, helps the detergent to be soluble in gasoline, or even other fuel or oil when the detergent additive is added to them.

The second component, a polar amine head, on the other hand, attracts and keeps impurities from depositing. These impurities range from water to metals to varnish to dirt.

The polar head has the ability to attract a diverse range of impurities and keep them afloat. Thus, preventing these impurities from forming deposits.

These impurities range from metals to salts to water to dirt. They are prevented by the deposit control additives from forming sludge, soot, oxidation products, and other deposit precursors from harming key engine parts.

#5: Other Additives

  • Oxygenates: These additives are added to reduce carbon monoxide and soot that is created during the burning of the fuel. Typically alcohols and ethers are used as oxygenating additives in gasoline.
  • Friction modifiers: A friction modifier increases the fuel lubricity and reduces friction at the engine components. Thus, increasing the fuel’s heat value for useful work at the crankshaft. A friction modifier may be added to the gasoline as a separate additive or in combination with a detergent additive.
  • Combustion improvers: A catalyst additive can enhance the combustion of fuel in the engine. The combustion improvers are typically made of fuel-soluble organometallic compounds or complexes of iron intended to improve fuel combustion.
  • Drag reducers: This is applicable for gasoline transported through pipelines. Viscous drag experienced in the pipeline is the limiting factor for pipeline capacity and hence, drag-reducing additives are used to improve higher-capacity transportation.
  • Anti-icing additives: Free water molecules in the fuel can freeze up at low temperatures. The formed ice crystals can choke fuel pipes and valves and hinder fuel flow. Anti-icing additives are added to avoid freezing since they lower the freezing temperature once mixed with water.
  • Dyes and markers: Coloring additives are used to differentiate a product, quality, and the properties of the fuel. Coloring matters. And helps in identifying the gasoline quality and properties. Markers are invisible. They develop color in presence of another reagent. Markers help in identifying the presence of other characteristics in the fuel.

Related Questions

Are gasoline additives worth it?

Gasoline additives are definitely worth it. They help in improving fuel combustion, reducing the deposits formed in the engine components, maximizing power output, and overall improving engine health and durability.

Gasoline additives are already added by the refiners and retailers themselves. The gasoline you fill for your vehicle in the gas station already has additives added to them.

But, if you want to address specific issues like engine knocking or deposits in your vehicle, you can add corresponding additives to the gasoline to address the issue.

Can gasoline additives damage the engine?

Gasoline additives do not damage the engine. These additives are added to gasoline specifically to enhance fuel combustion as well as reduce any negative impact of gasoline on the engine components.

Be it reducing the deposit formation, reducing knocking, improving flow, and combustion, or preventing rust formation – additives help gasoline to improve combustion with as minimal damage as possible.