Lubricants primarily consist of base oils, making up about 90% of their composition. These base oils form the foundation of lubricants, while the remaining portion includes various additive packages that enhance performance.
No, base oils are derived from crude oil during the refining process. They are a byproduct, not the raw crude itself.
Base oils are obtained during crude oil refining, where hydrocarbons are separated based on weight. Lighter hydrocarbons are used for fuels like gasoline, while heavier hydrocarbons contribute to the production of base oils and bitumen.
Base oils are categorized into five groups: Group I, Group II, Group III, Group IV, and Group V.
- Group I: The least refined, processed through solvent refining. It contains less than 90% saturates, a sulfur content of 0.03% or higher, and a viscosity index ranging from 80 to 120. Temperature range: 0-65°C.
- Group II: Further refined through partial hydrocracking, making the oil clearer. It contains 90% or more saturates, has a sulfur content of 0.03% or lower, and shares the same viscosity index as Group I (80-120).
- Group III: Fully hydrocracked, offering the best petroleum-based quality. It consists of at least 90% saturates, a sulfur content of 0.03% or less, and a viscosity index exceeding 120.
- Group IV: Known as synthetic base oils, these are made from Polyalphaolefins (PAO) via synthesis. They exhibit excellent stability in extreme temperatures and feature highly uniform molecular structures.
- Group V: Any base oil not fitting into Groups I-IV, including naphthenic oils, polyalkylene glycols (PAG), biolubes, and esters. These are also considered synthetic oils.
Lubricant quality is determined by checking its viscosity and Total Base Number (TBN). These factors indicate its thickness, shear resistance, and ability to prevent acid and sludge buildup.
Viscosity measures a lubricant's resistance to flow at specific temperatures. If too thin, it fails to protect moving metal parts; if too thick, it struggles to reach tight spaces and may cause excessive heat buildup. Viscosity index represents how much viscosity changes with temperature. It is commonly measured in Saybolt Universal Seconds (SUS) or centistokes (cSt).
TBN (Total Base Number) indicates a lubricant’s ability to neutralize acidic byproducts. A higher TBN value means the oil can better counteract acid formation, making it crucial for engine oils.
- Pour Point: The lowest temperature at which oil remains fluid. It is vital for lubricants operating in cold environments.
- Flash Point: The temperature at which oil vapors ignite when exposed to an open flame. This ranges between 132°C and 327°C, reflecting oil volatility and consumption rate.
This notation classifies a lubricant based on standards set by the Society of Automotive Engineers (SAE) and the American Petroleum Institute (API). The ‘20W’ indicates its viscosity performance in winter conditions, while ‘50’ represents its viscosity at 100°C. The ‘SL’ grade meets API’s specifications for engine protection.
SAE (Society of Automotive Engineers) establishes numerical codes to classify motor oils based on viscosity characteristics, ensuring standardization in the industry.
API grades evolve periodically, incorporating the latest advancements in engine protection and performance. Similar to how new car models are introduced, API updates provide improved formulations to meet evolving industry needs.
- API grades starting with ‘S’ are for gasoline engines, while those beginning with ‘C’ are for diesel engines.
- Successive updates in API grades are denoted by advancing letters (e.g., SG → SH → SJ → SL → SM → SN for gasoline engines).
- Diesel engine grades have also progressed over the years, with the latest being CK-4, introduced in 2017.
For Gasoline Engines:
API (American Petroleum Institute) categorizes engine oils based on their performance standards. The latest API service category encompasses the properties of earlier categories and can be used in older engines where previous API grades were recommended. Vehicle owners should always refer to their owner’s manual before selecting an oil.
Below are the API service categories for gasoline engines:
- SN (Current): Introduced in October 2010, this grade offers enhanced protection against high-temperature deposits on pistons, better sludge control, and improved seal compatibility.
- SM (Current): Suitable for engines manufactured in 2010 or earlier.
- SL (Current): Recommended for engines built in 2004 or earlier.
- SJ (Current): Compatible with vehicles manufactured in 2001 or before.
- SH and older (Obsolete): Not advised for newer gasoline engines due to insufficient protection against sludge, oxidation and wear.
For Diesel Engines:
API also classifies oils for diesel engines based on emission standards, sulfur content compatibility, and overall performance. Always follow the vehicle manufacturer’s guidelines before selecting a grade.
- CK-4 (Current): For high-speed, four-stroke diesel engines meeting 2017 on-highway and Tier 4 non-road emission standards; surpasses CJ-4, CI-4 and CH-4.
- CJ-4 / CI-4 / CH-4 (Current): For engines meeting earlier emission standards, with EGR/after-treatment compatibility.
- CG-4 and older (Obsolete): Not recommended for modern diesel engines.
A monograde lubricant (e.g., SAE 40) performs well in moderate to high temperatures but lacks efficiency in cold conditions. In contrast, a multigrade lubricant (e.g., SAE 20W50 API SN) contains additives like viscosity index improvers and pour point depressants. These additives enhance its performance in both high and low temperatures, ensuring smooth fluidity in winter and summer conditions.
Engine oil can darken due to oxidation, heat exposure, and the presence of certain additives. While dark oil can still be effective, it may also indicate high heat, contaminants, or additives that naturally change colour with use.
Topping up oil is necessary only when the level reaches the minimum mark on the dipstick. If the oil level falls below this point, an immediate top-up is required to prevent engine damage.
Delaying an oil change leads to excessive friction between engine components, causing overheating and reduced efficiency. Over time this accelerates wear; if ignored completely, the engine may fail. Regular oil changes help prolong the engine's lifespan.
Refer to your car manufacturer’s owner’s manual for the recommended oil type, viscosity, and weight. Additionally, look for oils with quality certifications such as SAE and API to ensure optimal performance and engine protection.
Synthetic oil is a chemically engineered lubricant made from modified petroleum components or synthesized raw materials. It contains advanced additives to enhance anti-wear, anti-pollution and anti-corrosion properties, and performs exceptionally well in extreme conditions.
Semi-synthetic oil is a blend of synthetic and mineral oils. These oils offer better protection in high temperatures and heavy loads compared to conventional mineral oils while being more affordable than fully synthetic alternatives.
Oil additives enhance the performance and longevity of lubricants. They help tackle high temperatures, moisture, rust, corrosion, oxidation and sludge buildup, ensuring optimal engine function under various conditions.
- Viscosity Index Improvers – Maintain oil thickness at different temperatures.
- Detergents – Prevent deposits and corrosion, keeping engine parts clean.
- Dispersants – Keep solid contaminants suspended to prevent sludge formation.
- Anti-Wear Agents – Protect metal surfaces when the lubricating film breaks down.
- Friction Modifiers – Reduce internal friction to improve fuel efficiency.
- Pour-Point Depressants – Prevent wax particles from solidifying in cold temperatures.
- Antioxidants – Slow down oxidation, preventing oil thickening.
- Foam Inhibitors – Reduce foaming caused by the crankshaft whipping through oil.
- Rust & Corrosion Inhibitors – Shield metal components from moisture and acids.
Recycled oil is used oil that has undergone filtration to remove impurities. However, it does not undergo chemical purification, making it unsuitable for high-performance engines. It is often reused in non-critical applications or as industrial fuel.
Re-refined oil undergoes extensive processing, including distillation and dehydration, to remove all contaminants. The purified base oil is then blended with fresh additives to create new, high-quality lubricants that meet API standards.
- Appearance: Virgin oil is clear and consistent.
- Smell: Recycled oil may have a strong sulfur or perfume-like odor.
- Color: Virgin base oils are usually lighter, while recycled oils are darker (though not always).
- Residue: Virgin oil should not leave sediment at the bottom, whereas recycled oil might.
Many dealerships also own lubricant brands and insist on using their own products. However, laws in several countries prevent dealerships from voiding warranties based on lubricant brand usage, ensuring customers can choose the best lubricant for their vehicle.
Recycled lubricants make up a large share of the market due to their lower cost and higher profit margins for sellers. Consumers often remain unaware of the lubricant quality used, and some regions lack regulations to distinguish recycled from virgin oils.
Recycled oils oxidize faster and may still contain impurities that can cause long-term engine damage. Engines using recycled oil generally have a shorter lifespan compared to those using virgin-based lubricants.
Synthetic oils undergo complex chemical synthesis, involving multiple refining and purification steps. This process enhances performance and durability, making them more costly than mineral-based lubricants.
Bharosa Desh Ka
