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Gasoline additives

All about gasoline additives

Gasoline is a blend of around 150 different components. The exact formula depends on the individual refiner based on their refining abilities, the market prices of the individual components, the time of year (winter or summer formulas), and the region (altitude and air quality regulations in the region). The base gasoline is delivered to a local terminal where each gasoline seller adds their own specific gasoline additives package. Those additives are:

Deposit Control Gasoline Additives

Deposit Control Additives keep the entire engine fuel system clean, from the fuel tank to the combustion chamber. Their main goal is to prevent the formation of deposits, particularly on intake valves and fuel injectors. If those deposits are allowed to form, they can interrupt and slow the flow of air and fuel flow through the engine, thereby reducing performance and efficiency and increasing emissions.

Common deposit control additives

Amides, amines, polybutene succinimides, polyether amines (PEA) , polyolefin amines and Mannich amines. Poly isobutene amine (PIBA)

How Deposit Control Additives Work

Deposit Control Additives work by forming a protective film on metal components to prevent deposit
precursors from forming. They tolerate the high temperatures and pressures within the engine. The deposit control additives in gasoline are intended to be used on a continuous basis to avoid deposit
build-up in the first place. However, they can also be used to remove deposits that may have formed prior to their use.

Deposit control additives are combined with fluidisers as a carrier component to prevent deposit buildup on valve stems

Fluidisers / Carrier Oil Gasoline Additives

High viscosity deposits can form at the intake valve stem and valve guide during cold weather. When that occurs, one or more intake valves can stay open, because the compressed valve spring can’t close the valve in time to allow cylinder pressures to rise. That results in cold weather starting problems. Carrier fluids are used to reduce valve sticking and ensure that engine valves operate properly in cold weather.

Carrier oils are used in conjunction with deposit control additives (DCP) to help combusted particles run off the hot metal surface of inlet valves and to help the DCP prevent deposit formations.

Common Fluidisers/Carrier Oils

Fluidisers / Carrier Oils are thermally stable structures such as Poly-Alpha-Olefins, Poly-Ethers, Poly-Glycols or heavy esters. Synthetic polyether derivatives such as Poly-Propylene-Glycols and Poly-Butylene-Glycols.

Friction Modifier Gasoline Additives

Friction modifier additives reduce power loss from friction due to the viscous drag of lubricant in the film separating the moving parts of the engine. Friction modifiers reduce viscous drag while maintaining the critical boundary lubricant film.

How Friction Modifiers Work

Friction modifier additives work by attaching to metal surfaces like cylinder walls and piston ring surfaces. They reduce viscous drag in the lubricant film on these metal surfaces by helping metal surfaces slide past each other more easily. The lower friction and reduced film drag results in improved engine power and increased fuel economy.
Glycerol Mono-Oleate is a common friction modifier

Corrosion Inhibitor Gasoline Additives

Water forms as part of the combustion process. Water condensation occurs in the crankcase as a result of temperature differences, and water can be introduced via the gasoline itself. Any water in the gasoline, tank, or engine can combine with air to attack iron and other metallic surfaces. Corrosion of ferrous metals causes rust formation, and water can cause other metallic surfaces to deteriorate. Rust can clog fuel filters, fuel lines, and fuel injectors and can degrade fuel pumps.

How Corrosion Inhibitors Work

Corrosion inhibitors like Dodecenyl Succinic Acid adhere to metal surfaces to form a protective film.

Antioxidant Gasoline Additives

Gasoline often contains unstable olefins and dienes. Those components can oxidize to form gums that flow through the fuel system, leading to fuel injector fouling and cause intake valve deposits.

How Antioxidant Additives Works

Antioxidants work by decomposing peroxides and by acting as free radical traps. Hindered phenols, for example, intercept free radicals to form stable hindered radicals that do not propagate further.

Conductivity Improver Gasoline Additives

Static electricity can accumulate in fuel during pumping operations. The problem can occur at refinery terminals or at filling stations. Static electricity is exacerbated by flowing the fuel through a pipe reduction, particularly an in-line filter located at the pump filler hose.
Static discharges present a fire hazard which can be reduced by improving the electrical conductivity of the fuel and by dissipating the electrostatic charge. Conductivity additives are often used in fuels of intermediate volatility such as low sulfur gasoline and diesel fuels

Commonly used Conductivity Improvers

Fuel-soluble chromium and proprietary combinations of polymeric sulfur and nitrogen compounds, quaternary ammonium salts, or complex organic alcohols.

Metal Deactivator Gasoline Additives

Soluble metal salts present in gasoline promote instability in the fuel by catalyzing the oxidation reactions, enhancing gum formation and deposit build-up in the fuel system and on intake valves. Copper is particularly associated with instability in fuels; its presence in the form of a soluble salt even at very low levels can markedly reduce fuel stability resulting in the adverse effects described.

How Metal Deactivators Work

Metal deactivators react with the dissolved metal in the fuel to form a stable chelate

Copper / Silver Corrosion Gasoline Additives

The sensors used in the fuel tank, lines and fuel rails contain copper and silver. Sulphur in gasoline can corrode non-ferrous metals and silver and silver alloys used in these sensors.

Thiadiazole additives form a film on these metal surfaces to prevent sulfur from reacting with the surface.

Octane Booster Gasoline Additives

Octane boosters raise the fuel’s octane and reduce detonation and knock. The need for octane boosters has been diminished over time as refiners have reconfigured the blending process to include naturally high octane components.

Ferrocene and methylcyclopentadienyl manganese tricarbonyl (MMT).

Demulsifiers / Dehazers / Emulsion Preventatives Gasoline Additives

Water can be present in fuel anywhere in the distribution system or the vehicle. When the gas/water combination is agitated, it forms an emulsion that can clog fuel filters, promote microbial growth and corrosion and create a hazy appearance.
Dehazers break up the emulsion so the water can be removed. Demulsifiers also break up emulsion formations in the fuel’s fluidizers/carrier oil components and reduce emulsion formation in the first place.

How Demulsifiers / Dehazers / Emulsion Preventatives Work

They modify the interfacial tension viscosity or film elasticity of water droplets within a fuel emulsion. This allows coalescence and separation of the water droplets from the fuel.
Phenolic resin alkoxylate is a common demulsifier

Anti-Valve Seat Recession Gasoline Additives

In older engines, exhaust valve seat metallurgies such as soft cast iron can be eroded through the repeated closing and opening contact with the hot exhaust valve. Erosion had been reduced by the use of lead alkyl antiknock additives. With the elimination of lead as a fuel additive, valve seat erosion in older engines increased. Newer anti-valve seat recession additives now provide protection from valve seat erosion in older engines operated on unleaded gasoline.

How Anti-valve seat recession (AVSR) additives Work

The additives deposit a thin protective layer on exhaust valve seat surfaces, preventing the metal-to-metal contact which lies at the heart of the erosion process.

Posted on by Rick Muscoplat

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