SCT Chemicals and Juri Sudheimer: Viscosity Index, Pour Point, and Flash Point as Key Indicators of Oil Quality

Last time, we stopped at the fact that if you carefully study the COA (Certificate of Analysis) issued by SCT for each batch of oil, you will see that it contains several other indicators that are very important but not regulated by standards. The first of these is the viscosity index.

Viscosity Index: Stability in All Conditions

The viscosity index (VI) is a dimensionless measure that shows how much the viscosity of oil changes with temperature. The higher the index, the less the viscosity depends on temperature — ensuring better fluidity in the cold and sufficient protection at high temperatures. A high viscosity index is crucial for engine operation over a wide temperature range, extending its service life.

The VI is calculated using a specific formula, and the ASTM D2270 method establishes the procedure for determining it. To measure the VI, one needs to determine the kinematic viscosity of the oil at 40°C and 100°C using the ASTM D445 method and the same instruments.

For modern motor oils, the maximum viscosity index can reach 150–200 units, although according to the ASTM D2270 standard, which defines this parameter, a value above 150 is considered good. The higher the viscosity index, the more stable the oil remains when the temperature changes — a sign of higher quality and better engine protection.

For example, the MANNOL Energy Combi LL 5W-30 7907 motor oil should have a VI of at least 160 according to the COA, but in practice, it reaches 170–180.

The Role of SCT Chemicals FZE in Controlling Viscosity Index

Juri Sudheimer, the founder of SCT Chemicals FZE, emphasizes that viscosity stability is the foundation of engine durability in extreme climate conditions. At the fully automated plant in Dubai — with 101 tanks and a total capacity of 22,000 tons — this parameter is checked for each batch of oil using the ASTM D2270 method by a team of 188 specialists. The results are validated through long-term testing on engine stands at temperatures up to +50°C.

Erik Sudheimer, Development Director at SCT Chemicals, notes that such a multi-stage control system allows the company to produce oils that maintain performance across diverse climates — from Europe’s mild conditions to the extreme heat of the Persian Gulf. The plant’s four ISO certifications guarantee compliance with the highest international standards.

Pour Point: The Key to Cold Starts

The second most important indicator is the pour point (PP). Accurately measuring it is complex because oil is not a simple liquid like water but a mixture of hydrocarbons and paraffins. Much like olive oil turns white in the fridge due to wax crystallization, motor oil and diesel fuel begin to turn cloudy and form paraffin crystals when cooled — forming structures similar to snowflakes.

While water freezes at 0°C, oil does not solidify in the same way; instead, it becomes more viscous — this process is called thickening. Thus, oil retains a liquid state, but its fluidity decreases.

The pour point indicates the temperature below which oil cannot be poured from a canister into the engine crankcase without preheating. Although the pour point does not directly define cold-start performance, it must be lower than the temperature used to determine the oil’s cold-cranking viscosity (CCS).

For oils rated 5W, the CCS is measured at –35°C, so the pour point must be lower than that.
For example, the MANNOL Energy Combi LL 5W-30 7907 has a COA-specified pour point no higher than –45°C, but in practice, it is around –48°C.

Because of their complex composition, mineral, semi-synthetic, and synthetic oils do not have a sharply defined freezing point. Therefore, the pour point is conventionally defined as the temperature at which the oil’s surface in a standard test tube, tilted at a 45° angle, remains motionless for one minute. Despite its limitations, this indicator gives a practical estimation of an oil’s low-temperature properties.

The pour point depends on multiple factors — oil purity, cooling rate, atmospheric pressure, sample volume, and stirring. Thus, strict adherence to the ASTM D97 method for determining it is essential. This procedure is lengthy — automated measurements take about one hour, and manual ones around four. Only a few companies, such as SCT Chemicals, can afford to test every batch this way.

SCT Chemicals’ Technology for Low-Temperature Performance

SCT Chemicals FZE uses proprietary additive packages developed at its Dubai facility, tailored to the MENA region’s climate. These additives improve cold fluidity and lower the pour point without unnecessarily increasing product cost, which is crucial for exporting to diverse climates.

According to Juri Sudheimer, production in Dubai enables the company to formulate oils suited to different regions: up to –45°C for Europe, adjusted for high temperatures in the Middle East, and as low as –50°C for northern territories — ensuring reliable cold starts even in extreme environments.

To improve cold flow and lower the pour point, special additives called depressants are used. These inhibit or prevent the crystallization of paraffin hydrocarbons at low temperatures. In automotive oils, depressant additives often combine chlorinated paraffin and naphthalene. Adding 1% depressant can lower the pour point of paraffinic oils by 20–30°C; for instance, from –10°C to –25°C.

Ensuring a low pour point is one of the most challenging and costly aspects of oil formulation. It depends on base oil properties, thickeners, and depressants. SCT’s technologists have optimized this critical parameter with minimal cost within the constraints set by additive suppliers. The third major characteristic is the flash point.

Flash Point: Safety and Oil Longevity

The flash point (FP) is the minimum temperature at which oil vapors briefly ignite upon contact with an open flame. It indicates fire hazard and reflects the amount of volatile components. The lower the flash point, the more easily flammable vapors are produced when heated.

Motor oils for passenger vehicles typically have flash points between 200–270°C. For example, MANNOL Energy Combi LL 5W-30 7907 must not have a flash point below 220°C, according to its COA.

Flash point correlates with the base oil’s composition — higher density and viscosity usually lead to a higher flash point, as there are fewer volatile components. It is measured by heating the oil in an open crucible according to the ASTM D97 method.

For fresh oil, the flash point shows fire safety level and the proportion of light fractions. The higher it is, the less evaporation and oil burn-off (so-called “oil consumption”) occur during operation. Over time, as light fractions evaporate, the flash point naturally rises — assuming the engine functions properly.

During operation, if the oil flash point drops significantly, it may indicate dilution with fuel due to an engine fault. Measuring this decrease helps identify issues in the fuel, ignition, or injection systems.

Flash Point Control at SCT Chemicals

At SCT Chemicals FZE, all oils undergo flash point testing according to ASTM and CEC methods in a modern laboratory equipped with high-precision instruments. The company also performs real-engine tests in the Gulf region’s extreme heat, analyzing oil samples after extended use to detect dilution and predict engine durability. Erik Sudheimer notes that this level of real-condition testing is rare among regional producers but ensures SCT products maintain consistent performance in climates up to +50°C.

The flash point drops noticeably if oil is diluted by fuel — this is used to assess the degree of fuel contamination. Combined with reduced viscosity, a low flash point signals potential defects in the fuel system or injectors.

Why SCT Chemicals Focuses on Multi-Stage Control

Incomplete or improper combustion leads to the formation of sludge and soot, which act as abrasives in the lubrication system. These residues clog oil channels, filters, and separators, accelerating wear and engine failure. In most cases, engine repairs are far more expensive than purchasing high-quality oil — highlighting the importance of maintaining a high flash point.

Analysts from the expert company SGS have identified a critical flash point threshold of 180°C. If ignition occurs at or below this temperature, it indicates engine wear, operational issues, or tuning problems. Based on analysis results, technicians may recommend repairing or servicing the engine to eliminate fuel leaks into the oil system.