Once a lubricant blender makes the decision to change base stocks, the next question is which one to use. A variety of synthetic fluids are available, including polyalphaolefin, esters, polyalkylene glycols and more. These are relatively expensive, though, so by far the most common choices are two highly refined grades of mineral base oil – Group II and Group III.

A number of factors go into base stock decisions – the type of lubricants to be made, their performance properties, raw material cost, storage tank availability and proximity of suppliers. Blenders in North America and Japan have had years of practice choosing between Group II and III, thanks to both grades being readily available in the market. Europe, on the other hand, has historically had very little Group II capacity, making Group III the dominant alternative to Group I. Recently, however, Chevron has made a big push to promote imported Group II, and rerefiners now offer a significant amount of the same grade.

To help flesh out the differences between the two grades, LubesnGreases submitted a series of six questions to four companies – Group III suppliers Neste and SK Lubricants, Chevron and Puralube, Europes largest rerefiner and a manufacturer of Group II. Following are their comments.

API defines groups I, II and III according to viscosity indices and sulfur and saturates levels. Group I oils contain more than 0.03 percent sulfur and/or less than 90 percent saturates, while groups II and III must contain no more than 0.03 percent sulfur and at least 90 percent saturates. Group I and II oils have VIs between 80 and 119, while VIs of Group IIIs must be at least 120.

What viscosity grades do you offer?

Holmquist. Six grades: 2, 3, 4, 5, 6 and 8 centiStokes.

Kim. We offer three Group III grades: a 4 centiStoke, a 6 cSt and an 8 cSt. We also offer a 3 cSt oil that is Group II.

Wadle. Three grades: 3, 5 and 8 cSt

Outhwaite. 4, 6 and 12 cSt Group IIs and a 4 cSt Group II+.

What benefits do your base oils offer? Can they serve as sole premium base stock, or will others be needed to make certain lubes?

Outhwaite. Our base oils are highly saturated, so they can impart good additive response. They contain practically zero sulfur (less than 10 parts per million), which makes them ideal for automotive formulations with low and medium levels of SAPS [sulfated ash, phosphorus and sulfur]. They possess excellent oxidation characteristics (NOACK volatility ranging from 2 percent to 26 percent) versus traditional base oils, enabling extended lubricant life.

Wadle. The main benefits of our oils are high viscosity index (105-115), excellent Noack volatility (1.5 percent to 9 percent) and constant availability at fair pricing.

Kim. Our Group III base oils have inherently high viscosity index (122-131), low volatility (6.5 to 15), excellent oxidation stability and excellent low temperature properties (pour point between minus 12 and minus 15) due to very severe hydroprocessing. They can serve as sole premium base stock.

Holmquist. For example, in European top tier formulations such as 5W-30, the lubricant blender benefits by using a blend of 4 and 5 cSt products as it will give very low Noack (2.5 percent to 37 percent) and excellent cold-cranking properties compared to a formulation using standard 4 and 6 cSt base oils. Our base oils can serve as sole premium base stocks.

Identify the ideal or one of the best applications for your base oils. Describe a typical formula for that product.

Kim. The best applications for our base oils are premium engine oils – both for passenger cars and for heavy-duty diesel trucks – and automatic transmission fluids.

Holmquist. A European 5W-30 fuel-economy passenger car engine oil can be formulated by using our 4 and 5 cSt products. The additive treat rate for this formulation is about 20 percent.

Wadle. The ideal applications for our thin grades are cutting oils in the metalworking sector. Our medium grade should be used in a 50-50 base oil blend for mid-SAPS 10W and 15W heavy-duty engine oils meeting the ACEA E9 specification. We recommend the same oil as the sole base stock in a 10W-40 ACEA A3/B4 or API-SL passenger car motor oil. Additive treat rates typically range from around 10 percent dispersant plus 8 percent viscosity index improver for mid-SAPS heavy-duty engine oils to 11.5 percent DI package plus 15 to 17 percent for viscosity index improver.

Outhwaite. The highly saturated nature of Group II base oils versus [Group Is] enables some good response to dispersant chemistries, which, combined with excellent oxidation characteristics, can enable some optimization of additive treat rate for certain performance tiers such as ACEA E7 heavy-duty oils. The low sulfur content of Chevron Group II oils makes them an ideal component for low- and mid-SAPS applications, where Group Is cannot be used and cost savings can be achieved versus Group III oils.

Ultra low-viscosity or low-volatility lubricants, typically 5W or 0W grades, will require the use of Group III or above base oils, depending on the required specification.

Describe the finished product mentioned above. Would performance be standard or premium?

Outhwaite. Our 6 cSt oil is ideal for the core base oil in heavy-duty motor oil formulations. It typically is the single base oil required for 15W-40 ACEA E7 or E9 type formulations, and it can be blended with our 4 cSt Group II+ or a 4 cSt Group III to make cost-effective high performing 10W-30 or 10W-40 heavy duty oil. The 6 cSt oil is a qualified component in 10W-30/40 ultra-high performance diesel engine oils that meet ACEA E6 or E4 standards, enabling cost optimization of the base oil blend.

Wadle. Puralube base oils are predominantly used in standard 10W-30 and 10W-40 motor oils. They may also be used as a 10 percent base oil interchange in premium ultra-high performance heavy-duty diesel oils.

Holmquist. It is a premium product with very competitive Noack volatility. We regard our 5 cSt product as premium quality base stock.

SK: The performance would be premium. The base stock allows lubricant blenders to have a wider range of flexibility with high VI for reduced treatment of VI improver, better Noack volatility (for lower oil consumption with improved fuel economy), excellent low-temperature properties including cold cranking simulation and oxidation stability for various engine tests. Also, it can help the reduction of SAPS contents in diesel engine oil for the purpose of protection of after-treatment devices such as diesel particulate filters.

What advantage do your base oils have over Group II oils? Discuss products that can be made, the quality of those products, economics and/or logistics.

Holmquist. European top-tier passenger car engine oils, for example a 5W- 30 oil, require full Group III base stocks. This is because Group III has lower Noack volatility, enhanced cold temperature properties and better thermal stability compared to Group II. Such a lubricant cannot be formulated with only a Group II base stock. The blender benefits also for not having to add new storage tanks since Group III can be used in several formulations for engine oils, driveline oils and even in industrial oils. The quality requirements for top-tier formulations are increasing continuously.

Kim. The main difference between Group II and Group III is viscosity index. With higher viscosity index, Group III allows lubricant blenders to meet the most stringent engine oil specifications without blending PAO, especially those lower-viscosity, fuel-efficient engine oils, without compromising engine durability.

What advantage do your base oils have over Group III oils?

Wadle. Group III oils are priced more expensively, and Group III logistics are also higher. Approximately 90 percent of standard lubricating oils in Western Europe can be made with Group II base stocks. Puralube base stocks have an advantage in terms of sustainability since they are rerefined.

The development costs for premium products are currently far too expensive for an independent new-comer company like Puralube.

Outhwaite. Our Group II base oils can be used in a far wider range of lubricant applications than Group III base oils – more than 90 percent of standard finished products. In addition to the heavy-duty motor oils discussed earlier, Chevrons 12 cSt Group II base oil can be used in higher viscosity industrial oils (for example ISO 68 and 100 fluids) without the need for unconventional components.

Chevron Group II base oils are part of a global product slate, currently produced at two refineries with a third production unit scheduled to come on line in October 2013. This provides increased supply security. The Chevron global product slate does enable global formulations that can reduce complexity and development costs for pan-regional organizations, while also allowing regional players to meet global standards.

For a blender making the usual span of automotive and industrial products looking to reduce the number of base stock SKUs that are bought, which base stocks are the must-have grades?

Wadle. We believe a blender in Western Europe must have the following base oils.

for Group I, a solvent neutral 150, an SN 500 or 600 and a bright stock;

for Group III, a 4 cSt and a 6 cSt oil, or a 5 cSt oil, depending on OEM approvals that are held;

for Group IV, a 4 cSt and a 6 cSt base stock;

for Group V, some esters with approvals.

For industrial applications, the following should be added: Group I SN70 and SN100, a 3 cSt Group III and some white oils. Group IIs are optional.

As Group I capacities continue to disappear, Group II and III oils will replace Group I in more formulations.

Outhwaite. Given the growth of low- and mid-SAPS heavy-duty diesel engine oil and passenger car engine oil standards, and given the overall drive to increased performance specifications, which in turn requires the use of premium base oils, it is important that lubricant manufacturers act now to develop their medium- and long-term base oil strategies. This will help optimize inventory management and minimize complexity in the future. Our base oil range has been designed such that they are applicable for a wide range of automotive and industrial applications. The most likely must-have grade is our 6 cSt product, which offers the most versatility.

Kim. This is a difficult question to answer. We believe most blenders using SKs Group III oils at this stage have approvals for the OEM applications and therefore regard our oils as must-have products. This is especially true with our 4 cSt and 6 cSt products.

Holmquist. For blenders making automotive oils, the must-have Group III grades are 4 cSt to 6 cSt oils. For industrial products lighter and heavier grades are also needed.