| 17 August 2009
A lubricating oil expert shares his knowledge with readers of Road Ahead magazine.Fleet operators are advised to be aware of the significance of the various grades of lubricating oils available in the South African market, their performance characteristics and of the role of quality in making the right selection.In my experience, fleet operators and the motorists at large, do not always comprehend the true benefits of using higher-end lubricant products during servicing. Often this results in cheap, obsolete specification grades of oil being used, which is detrimental to both engine life and performance.
Fundamental to understanding how a lubricant works, is having a basic working knowledge of what makes a lube oil. Lubricating oils for trucks and automobiles, boats, heavy equipment, ships and aircraft all consist of two basic components, base oils and additives. The additive package consists of a variety of specialised chemicals designed to boost the performance and extend the life of the lubricant. However, it is of vital importance in the high-tech engines of today that the user should understand the importance of the base oil component, which typically makes up 90 – 95% of the blended lube oil. Indeed, the performance of the lubricant is affected by both base oil and additives. Additives assist in slowing the breakdown of the base oil, in modifying its viscosity and in providing extra protection to the working parts of the engine, in effect protecting and supporting the performance of the base oil component. It is a well-known fact that cheaper lubricants contain low quality base oils combined with low doses of additive packages. Using these cheap lubricants to save money makes false economic sense.
Engine rebuilds are very costly, coupled with the taking of the vehicle out of service for a significant amount of time. Therefore any lubricant which extends engine life makes excellent financial sense. In addition, high performance lubricant oils bring increased fuel economy, of great significance at today’s fuel prices, lower exhaust emissions and longer oil change intervals. This is why engine manufacturers have begun to specify high performance base oil stocks for lubricants to be used in the engines of today. Even earlier model engines of relatively low number of hours in service would benefit from a fill of such lubricants. The key to the quality and performance of a modern lubricant lies in the selection of high viscosity base oil stocks, a so-called High VI or HVI base oil. Base oils refined in the traditional way are called Group I base oils and arise from the refining of crude oil using conventional methods, technically referred to as solvent extraction and solvent de-waxing. They are typically honey-coloured, which indicates some impurity. Group I base oils are low in viscosity index and require special additives to raise their performance levels over the full operating temperature range. Advances, however, in refining technologies over the immediate past decades, have resulted in ultra-refining processes such as hydro-cracking and wax isomerisation has resulted in a class of base oils designated Group III. Certain international refineries also produce Group II base oils, a product of the lower order hydro-treating process, which is slightly earlier technology. Group II base oils, however, do offer improved characteristics such as sulphur levels and other impurities over Group I.
Over the last two decades, the evolution of synthetic lubricants has largely been based on the development of a class of synthetic base oils called the PAO (polyalpha olefins). PAO’s have the highest viscosity index and exhibit the greatest stability in use of all the base oils. They are arguably more correctly classified as chemicals, since they do not find their origin in the refining of crude oil. They were, however, the foundation for the development of a generation of highly effective synthetic lubricants, many used in high-stress applications such as aircraft engines, Formula 1 racing and industrial gearboxes. But they are very costly and as such, the major manufacturers of engines stopped short of specifying their use in initial fill and service fill lubricants across the board. Now, with the advent of Group III base oils, the situation is changing with many original equipment
manufacturers requesting Group III base oils initial fill and also in after-market products.
Group III base oils offer the lubricants technologist many of the advantages of the PAO’s, at a considerably reduced cost. They are as stable as PAO’s at high temperature, show excellent high viscosity index characteristics, low volatility and excellent oxidation
stability, meaning less tendency to break down in service. Along with Group II base oils, they are a brilliant water-white in colour, indicating a much purer composition than Group I.
| Class | Sulphur Content | Saturates | VI | Oxidation Stability | Volatility# |
| Group I | >0.03% | <90% | 80 -120 | 250* | 17 wt% |
| Group II | <0.03% | >90% | 80 -120 | ||
| Group III | <0.03% | >90% | 131 | 515** | 7 wt% |
| PAO | n/a | n/a | >120 | 533 | 7 wt% |
* Oxidation stability via Rotary Bomb Oxidation Test for base oil HT150N
** Oxidation stability via Rotary Bomb Oxidation Test for YUBASE 6
# Volatility using the Noack Test DIN 51581 – measures loss of oil in service due to consumption in the engine and evaporation.
Group III base oils sourced on the SK Refinery Korea and Group II base oils sourced on the S-Oil refinery, both in Korea have been available in South Africa in recent years due to a distribution agreement signed between the Koreans and Orbichem Petrochemicals of Cape Town. Already the major multinational oil companies with local oil blending plants have enhanced their product lines by tapping into the ready availability of the Korean stock. Group II and III base oils are ultra pure refined petrochemicals and in addition to their superb base lubricating properties, they are used in the healthcare environment in the manufacture of domestic products such as baby oil, liquid paraffin and petroleum jelly. The are water-white, odourless, tasteless and pour extremely well at a wide range of operating temperatures. In summary, fleet operators, operators of heavy industrial or mining equipment, owners of modern motor cars and owners of older vehicles with relatively low mileage can all benefit in terms of operating costs and in terms of efficiency by insisting on the use of
lubricating oils that are based on Group III base oil technology and no less.
Cliff Classen is a qualified chemist and petroleum technologist and is managing director of Orbichem Petrochemicals, based in Cape Town. Orbichem Petrochemicals is both independent and indigenous and is 100% black-owned, serving a highly technical market
dominated by multinational oil and chemical companies.