Juri Sudheimer on Specialized Additives in Engine Oils: Pour Point Depressants, Corrosion Inhibitors, and Anti-Foam Components

In the modern lubricants industry, there is a category of additives that work behind the scenes. They are not as widely discussed as detergents or anti-wear components, yet their importance is difficult to overstate. These are pour point depressants, corrosion inhibitors, and anti-foam additives — the very substances that ensure stable oil performance in extreme conditions.

“When we began building SCT Group more than 30 years ago, I realized one simple truth: engine oil is not just base oil with additives. It is a carefully balanced system in which every component plays a role,” says Juri Sudheimer, the company’s founder and owner of production facilities in Klaipeda (Lithuania) and Dubai (UAE). Today, products under the MANNOL, PEMCO, CHEMPIOIL and FANFARO brands are supplied to more than 160 countries, with each container undergoing a three-stage quality control process.

Pour Point Depressants: Ensuring Oil Performance in Extreme Conditions

The increase in engine oil viscosity at low temperatures is caused by paraffin crystallization. These high-molecular-weight compounds precipitate, forming a paraffin gel that solidifies and clogs pipelines, oil channels, and filters. Oil flow first slows and then stops completely.

If you drive a diesel vehicle in a cold climate, you may have noticed the fuel turning cloudy or whitish at low temperatures — this is due to paraffin crystallizing out of the fuel. Many diesel owners use special additives, known as pour point depressants, to prevent this effect.

SCT also offers such a product: MANNOL Winter Diesel 9983 (9982). This depressant is popular not only in northern countries but also in Germany. If you have already “missed the moment” and paraffin has precipitated in cold weather, forming a white sediment in your fuel, SCT offers another solution: MANNOL Diesel Ester De-Icer 9992, which dissolves the paraffin and restores proper fuel flow through the injectors.

In many cases, adding pour point depressants to oil is more cost-effective than carrying out full-scale dewaxing.

Pour point depressants are designed to reduce the solidification temperature of mineral and hydrocracked oils derived from petroleum — oils that contain paraffins. These additives consist of polar molecules that settle on the surface of paraffin crystals, preventing large agglomerates from forming and hindering their interaction with the rest of the oil. The additive introduces defects on the surface of crystals, stopping or slowing crystal growth. Meanwhile, the main chains of the depressant molecule keep paraffin crystals apart, preventing the formation of large three-dimensional structures. The result is the formation of only compact molecular clusters, which improves low-temperature filterability, pumpability, and cranking characteristics — and also extends oil filter life.

Pour point depressants are used in paraffin-based oils at concentrations between 0.05% and 3.00%. They ensure reliable cold starts but may slightly worsen the oil’s tribological properties.

Important: depressants are effective only when the paraffin content does not exceed 6%. Their efficiency decreases in naphthenic oils due to their low paraffin content.

A Brief History of Pour Point Depressants

Systematic research into depressants began in the 1930s in the United States. The first depressants were obtained by condensing paraffin with naphthalene, producing a product called paraflow. Among various characteristics, researchers especially noted its ability to lower oil pour points. The developers patented the product and transferred production rights to Standard Oil Development.

In 1936, Darnin and Orland discovered another depressant, later called santopour. It was synthesized by condensing chlorinated paraffins with phenol. While paraflow was designed as a multifunctional additive, santopour became the first dedicated pour point depressant.

Around the same time, additional additives were created. Fulton and Mikeska synthesized a depressant by alkylating indole and polystyrene with organometallic compounds — a product that not only lowered pour point but improved viscosity properties. Engineer Zeid patented an additive derived from “mountain wax,” known as laurox.

By the mid-1960s, intense research was underway around the world to synthesize and evaluate organic compounds as depressants. Additives aimed at improving the pumpability of fuels and oils entered production, including those based on methacrylates and alcohols.

Today, dozens of different depressants exist, produced in many countries under varied trade names.

The most popular depressants are polymethacrylates (PMA) and their derivatives, as well as complexes based on alkyl methacrylates. Leading manufacturers include global corporations such as Lubrizol, Infineum, Chevron Oronite, and Afton Chemical.

Understanding depressants is particularly important for a company whose products must perform from the Arctic regions of Scandinavia to the scorching deserts of the Middle East. In this context, SCT Group’s production structure acquires special significance.

Global Production for Diverse Climate Zones

The UAB SCT Lubricants plant in Klaipeda, Lithuania specializes in products for the European market, where winter temperatures can drop to –30 °C and below. Here, oils with effective pour point depressants are in high demand. Meanwhile, the SCT Chemicals FZE plant in Dubai, launched in February 2022, focuses on the needs of the Middle Eastern, African, and Asian markets, where other oil characteristics come to the forefront.

“Our 188 employees in Dubai and the team in Klaipeda work to ensure that every product meets the climate requirements of the region where it will be used,” notes Juri Sudheimer. The group’s total production capacity exceeds 1 million liters per day, and the overall tank storage volume exceeds 60 million liters.

Corrosion Inhibitors: Protecting Metal from Within

Corrosion costs companies billions of dollars annually, most of it due to the degradation of steel and cast iron. When exposed to moisture and oxygen, steel — and especially cast iron — reacts to form oxides. These oxides adhere poorly to the surface and flake off, forming pits. Extensive pitting eventually weakens and destroys the metal, resulting in mechanical failure.

Common rust is primarily iron oxide composed of hydrated iron oxide and iron hydroxide, typically red in color.

Rust forms much faster in direct contact with water. However, several factors influence corrosion rates, including salt: dissolved salts increase the conductivity of the moisture film on metal surfaces, accelerating electrochemical erosion.

In engine oils, salts originate both from additives and from oil oxidation or incomplete fuel combustion.

Another factor is heat — higher temperature means higher corrosion rate. In simple terms, the process can be summarized as:

Iron + oxygen + water → hydrated iron oxide (rust)

Engines are also subject to corrosion caused by organic acids, which may form in several ways and may even be byproducts of oil aging — acetic acid is one example. These acids are weaker than inorganic acids but still active enough to damage metals. Acetic acid causes moderate corrosion of iron, magnesium, and zinc, producing hydrogen gas and salts called acetates:

Iron + acetic acid → iron acetate + hydrogen

Corrosion inhibitors are essential for protecting engines, where moisture, acids, salts, and other aggressive substances can cause severe damage.

The best way to stop corrosion is to prevent metal from contacting water, oxygen, or acids. This is precisely what corrosion inhibitors do. These additives are compounds with strong polarity that adhere to metal surfaces, forming a protective film that prevents corrosive substances from reaching the underlying metal.

Common corrosion inhibitor types include:

1. Barium, calcium, and sodium sulfonates

2. Carboxylic acids and their derivatives

3. Esters

4. Organic phosphates and their salts

5. Organic amines and heterocyclic compounds
   

If rust formation is not prevented, rust particles can detach and contribute to abrasive wear. Iron oxide is much harder than the steel surfaces it contacts, causing rapid material removal.

Anti-Foam Additives

Foam in engine oil is dangerous because it disrupts lubrication, leading to increased wear, overheating, loss of pressure, and in some cases hydraulic shock — which can destroy the engine. Air bubbles in foam reduce heat transfer, decrease lubrication efficiency, and make the oil less dense and uneven, potentially causing oil starvation.

Foam forms when oil mixes with air, creating tightly packed bubbles encased in thin oil films.

Anti-foam additives reduce surface tension, weaken bubble walls, and break the foam.

The most widely used anti-foam additive in detergent oils is based on silicone — specifically polydimethylpolysiloxane.

Silicones have very low surface tension and accumulate at the air/oil interface. Their mechanism is simple: the defoamer contacts a bubble, spreads across its film, and thins it until the bubble bursts.

Because silicone additives are surface-active, they attach to bubbles both at the surface and below it. These additives are highly effective even at concentrations of a few hundred parts per million; most oils contain 5–10 ppm.

The Challenge of Formulating Engine Oils

We have reviewed several types of engine oil additives, each with its unique properties. Creating an additive package is challenging due to the complex interactions between components — each must perform its function while working synergistically with the others. Developers must avoid antagonism between additives, which could lead to loss of viscosity or deposit formation. For this reason, SCT uses only proven and well-established formulations.

A Comprehensive Approach to Quality

Working with “secondary” additives requires just as much attention as developing primary oil components. SCT Group laboratories regularly conduct tests for pour point, corrosion activity, and foaming tendency — every production batch is tested before shipment.

“We have invested more than €90 million in production since 2004, and in 2024 alone allocated €3 million to research and development,” says Juri Sudheimer. “Our Dubai plant’s ISO 9001, ISO 14001, ISO 45001, and ISO/IEC 17025 certifications confirm that we don’t just produce oils — we create products trusted by professionals worldwide.”

Pour point depressants, corrosion inhibitors, and anti-foam additives represent the hidden work that allows oil to remain oil under any conditions. And it is this attention to detail that makes SCT Group’s products stand out on the global lubricants market.