Why is Group I being phased out so quickly, and is this trend expected to continue? 

Simply stated, current lubricant standards are quite stringent. In order for finished lubricants to meet increasingly demanding performance requirements, they must be formulated with higher-quality base stocks. This has pushed base stock refiners to shift their attention and resources to the production of API Group II and Group III base oils. 

Figure 1. Group I Capacity Closures, 2015-2022

Because lubricant specifications will only become more rigid as emissions limits and fuel economy requirements tighten, it is expected that Group I capacity will continue to decrease in coming years. 

While the outlook for Group I base oils appears to be a bit grim, there may be one bright spot on the horizon. Differing from its solvent neutral counterparts in a few key ways, bright stock has managed to remain an important component in a variety of finished lubricant formulations. This has allowed demand for bright stock to stay relatively strong. In fact, Kline stated that bright stock demand has declined at a markedly slower rate than other Group I base oils, decreasing by just 9% since 2010.

What Is Bright Stock, and How Is it Refined?

Bright stock is a high-viscosity base oil—generally classified as an API Group I base stock. It is refined by running feedstock through a vacuum distillation process, which is followed by solvent extraction and solvent dewaxing. The oil is then run through a hydrofinishing process. This step subjects the oil to higher temperatures as well as higher pressure of hydrogen gas in order to break the double molecular bonds and force out free radicals. The whole bright stock refining process results in a base stock with higher quantities of purer hydrocarbon molecules. 

Bright stock can be produced in other ways, too. For instance, some companies use a refining process that is more similar to that used to produce Group II base stocks. This process employs hydrotreating and catalytic dewaxing of naphthenic crude oil.

Which Products Require Bright Stock?

According to an article written by Kline’s Kumar, bright stock is generally used to formulate mid- to high-viscosity lubricants. These include industrial gear oils, marine cylinder oils, process oils, greases and monograde engine oils. 

Bright stock has more or less been phased out of automotive engine oil formulations, however. The viscosity of modern passenger car motor oils has been pushed as low as SAE 0W-8 in the past several years, making heavy-viscosity bright stock a poor option for use in these types of finished formulations. 

Similarly, today’s automatic transmission fluids also boast low viscosity and therefore do not require bright stock. 

Demand Is Steady

Demand for bright stock has remained “pretty steady” during the past couple of decades, Laura Pottorf, global marketing manager, base stocks and waxes for ExxonMobil Product Solutions Co., told Lubes’n’Greases. “Maybe it’s up a little bit or down a little bit, but it has held pretty constant over a fairly significant time frame.”

Since bright stock demand in automotive lubricant applications has dwindled, how has overall demand for bright stock managed to hold steady?

“What has happened is that there are some places where bright stock was used in automotive applications,” Pottorf told Lubes’n’Greases. “Some of those old engine oil formulations have been retired, and you see that’s where Group II or Group III have been substituted in. But what has happened at the same time is that the use of bright stock in industrial and marine applications has kind of offset the other demand going away. That is what has held it about constant.”

How else has bright stock managed to maintain its place in the lubricants industry while demand for other Group I oils has faltered? 

According to Kline, there are three major reasons for the relatively consistent demand for bright stock:

• There are very few substitutes for bright stock available on the market right now. Because bright stock has a very high viscosity, producing it at a Group II unit comes with sizeable challenges. Furthermore, bright stock cannot be produced at a Group III unit. 
• Bright stock offers its producers with a higher margin than other Group I base oils do. This higher margin makes bright stock a more attractive option for Group I producers and provides a safety net of sorts for those producers looking to circumnavigate the challenges associated with the deteriorating Group I market. 
• Synthetic substitutes for bright stock are too expensive to be a viable option for many lubricant formulators. Polyalphaolefins and polyalkylene glycols tend to be quite spendy, and these Group IV and Group V base stocks are not currently produced in large enough quantities to completely fill bright stock’s place in the market. 

A feature article written for the April 2022 issue of Lubes’n’Greases magazine by Benny Cao, general commercial manager-grease for Lubrizol, and Carlos Nazario, North America project manager for Lubrizol, added a few more reasons that bright stock has maintained a strong position in the lubricants market. 

• Bright stock is compatible with other oils as well as additive packages.
• Bright stock boasts decades of proven high performance, which makes blenders and end users more comfortable with its use in finished lubricants.
• Bright stock can be used as a high percentage of finished lubricant formulations.

What Does the Future Hold for Bright Stock?

It is not a fluke that demand for bright stock has remained steady for many years. But will this steady demand continue in coming years, or will it see a significant decrease in the future?

“Frankly, even going forward, our view is that…right now based on what we currently know, we think that demand will remain in about that same range,” Pottorf told Lubes’n’Greases. 

Despite bright stock’s ability to hold its spot in an ever-changing market, it must weather some storms as the base oil market continues to evolve. The availability of bright stock is expected to decrease further as closures of Group I plants continue because some Group I facilities also house bright stock units. Fortunately, Kumar stated that there are two new bright stock units planned to come on stream by 2025. Both units will be housed in Group II refineries. 

In the meantime, lubricant formulators may need to figure out ways to stretch the existing supply of bright stock to meet all current needs. Kumar suggested that they could do this by reformulating lubricants using larger proportions of heavy neutral stocks. This could be challenging, though, because reformulating in this way could require the addition of a thickener or other additives. 

Furthermore, reformulation could affect original equipment manufacturer approvals and would require formulators to invest significant time and money into developing formulations that meet OEM requirements. The feasibility of bright stock substitution is also affected by other factors, including pricing and technical suitability for a given application. (For more on bright stock alternatives, check out Trevor Gauntlett’s feature article in the November 2021 issue of Lubes’n’Greases magazine.)

New base stock technology may change the substitution game, though. ExxonMobil recently announced an expansion at its refinery in Singapore. The expansion will usher in the production of “an extra-heavy-viscosity base stock” to the market. The company stated that the expansion is expected to include up to 6,000 barrels per day of this new base oil, which will be referred to as EHC 340 Max. 

“We plan to market EHC 340 Max globally,” Pottorf told Lubes’n’Greases. “It will be produced in Singapore but will be available globally.”

Might this new base stock be a viable substitute for conventional Group I bright stocks? ExxonMobil believes that it could be. 

“When we look at the properties of this material, it has got some capabilities and some qualities that are different than a conventional Group I bright stock,” Pottorf said. “It’s got better low-temperature performance; it’s got a high viscosity index; it still has an extra-heavy viscosity range in line with a Group I bright stock; it’s got a high flash point, which can be very important for high-temperature applications as well. So when we look at our overall EHC base stock slate, this extra-heavy-viscosity base stock is really going to fill out the full range of that slate, and we think it will even widen the coverage that we have across a very broad range of applications. In some cases, we think that EHC 340 Max will get into applications where Group I bright stock can’t be used today.”

Another benefit of this potential bright stock alternative is increased efficiency in certain applications. “In some cases, we think that [EHC 340 Max] will make the use of bright stock more efficient,” Pottorf said. “There is a range of different ways that we think it can be used. Some of the primary applications, though, are in automotive and industrial gear oil, but there are others as well.” 

Will this new base stock—and others like it—phase out bright stock completely? While it is impossible to know for sure, Pottorf believes that the two base stocks can exist in harmony rather than in competition with each other. “We think it complements our existing Group I bright stock,” Pottorf said. “We believe there is a place for both” in the market.  

Sydney Moore is managing editor of Lubes’n’Greases magazine. Contact her at Sydney@LubesnGreases.com