Now a German research organization and a U.S. chemical giant are hoping to break that barrier.

BAM Federal Institute for Materials Research and Testing and Dow Chemical claim to have improved PAG oxidative stability through a combination of processing changes and additive technology. Following successful testing, field trials of PAG engine oils are taking place this year, and commercialization could be just two years away.

This is something that has moved beyond the scientific or research stage to the demonstration stage, Mathias Woydt, head of BAMs Tribology and Wear Protection Subdivision, said during an interview with LubesnGreases. If things go as we expect, we could see [automakers] begin using engine oils made with polyalkylene glycols for factory fill within two years.

Woydt, who has studied PAGs for nearly two decades, said its not that they have had poor oxidation resistance; in applications such as gear oils, they are stable enough to allow extended drain intervals and to tolerate high operating temperatures. The problem, Woydt said, is that, in the past, performance petered out in the difficult conditions of automotive crankcases. PAGs could not match the oxidation resistance of mineral base oils and were unable to provide drain intervals demanded by original equipment manufacturers.

According to Woydt, BAM and Dow Chemical managed to address that shortcoming during the middle of the past decade. From 2005 to 2006, through a series of five research projects funded by the European Union and Germany, they discovered that a change in the manufacturing process could produce a PAG with improved oxidative stability. In addition, researchers developed chemical additives that worked with that PAG to further improve oxidative stability.

Since then we have improved it further and now are at least meeting the oxidative stability of polyalphaolefins, Woydt said, referring to another type of synthetic base stock that is commonly used to formulate high-performance lubricants, including engine oils.

At the OilDoc Conference in Rosenheim, Germany, in February, Woydt said that engine oils formulated with two Dow PAGs – propylene glycol monobutyl ether and polybutylene glycol monobutyl ether – exceeded Class 3 performance on a TOC bench test for oxidative stability. This would correspond to a drain interval of more than 30,000 kilometers in turbodiesel engines with particulate filters. In road tests, he said, the same formulations provided acceptable performance with intervals of more than 40,000 km.

Dow provided the PAGs for the work that has been done, and developed additive technology to use with them. Dow declined to discuss the processing change or to disclose information about the additives.

If PAGs can meet expectations for oxidative stability, they will bring numerous attributes to the crankcase. A combination of excellent lubricity and high affinity to metal means that these fluids can reduce friction while protecting moving components from wear. As a result, Woydt said, it is possible to use PAGs to formulate engine oils at lower viscosities than would be possible using mineral base oils while keeping volatility acceptably low.

At the OilDoc meeting, Woydt reported engine test results in which PAG engine oils exhibited up to 3 percent improvement in fuel economy compared to a 5W-30 oil formulated with PAO base stock. He added that other tests have showed PAG friction reduction is especially strong when engines are idling, suggesting a particular improvement in fuel economy for urban driving.

Fuel economy is such a big push for OEMs now, Woydt said. A lot of what the lubricant industry has been doing to try to help with that has been to use lighter oils. I think its evident that they are approaching the limits of how low they can go with mineral base oils. But with PAGs they could continue to reduce viscosity even further. He suggested that PAGs would allow formulators to make 5W-5 engine oils that still protect engines. Being thinner than 5W-30 or 5W-20 oils, 5W-5s would presumably create less friction and allow better fuel economy.

Dow believes that the unique properties of PAG-based advanced lubricants allow a fuel economy improvement, even at the same high-temperature/high-shear viscosity as traditional conventional and synthetic engine oils, said Chuck Carn, lubricants global strategic marketing manager at Dow. In addition, Dow believes that the unique properties of its chemistry enable very high viscosity index – above 220 – low-viscosity engine oils with very low volatility and oil consumption. We believe this is a unique value proposition that can offer 2 to 5 percent fuel economy improvement depending on formulation, OEM and reference oil, without negatively impacting engine durability.

Another change with PAGs, Woydt said, is that they require different additives and fewer additives than mineral base oils do when formulating engine oils. For example, PAGs have such high viscosity index that they need little or no viscosity index improver. It is also possible to formulate a PAG engine oil that is free of metals and ash. As a result, PAG engine oils would not poison emissions control technolgies as do mineral oil based fluids that contain additives such as antiwear agent zinc dialkyldithiophosphate.

PAGs can also impart excellect low-temperature pumpability, Woydt said, and tests have shown them to be non-toxic to aquatic species and biodegradable according to European standards.

To date, Woydt said, no engine oils based on PAGs have ever been commercialized. But it is not a niche application that he and Dow envision.

This is something that has been pushed by OEMs because they want it, he said. Commercialization may begin with one or two companies using them in one model, but once they see that [PAG engine oils] work, I think that numerous OEMs will use them in multiple models.

Dow officials sounded even more effusive.

The automotive lubricants market is approximately 20 million tons globally, Carns said. This represents an enormous opportunity for Dows chemistry. The balance of emission regulations, fuel economy tax implications and fuel costs have tipped in our chemistries favor. We believe now is the time where the market will move from refined oils to designed chemistry for base stocks.

Two field trials were scheduled to begin before the end of summer. One is being conducted by Ford on passenger cars under a U.S. $1.2 million (834,000) grant from the U.S. Department of Energy. Dow is a sub-awardee in that program. Woydt said the other trial is being conducted by a European truck manufacturer, but he declined to identify it. Assuming the fluids pass their field trials, both OEMs could begin using them for factory will within 12 to 24 months, he said.

Woydt predicted that adoption of PAG engine oils will not be restricted by capacity to make the base stocks. According to LubesnGreases research, global capacity is more than 900,000 metric tons per year. But Woydt said this number could increase several fold based on capacity for PAG building blocks.

Its not like demand [of PAG engine oils] is going to start off at 1 million tons per year, Woydt said. If youre talking about one or two models, initial factory fill volumes will be much lower. Then as demand grows producers can add capacity needed to keep up.

Currently PAGs are significantly more expensive than mineral base oils, but Woydt said he does not expect that to pose a significant hurdle, either. That incremental cost, he said, pales in comparison to the potential penalties that OEMs face in coming years if they fail to meet carbon dioxide emission caps set by governments.

The fuel economy gains easily finance the additional filling costs of using PAGs, he said. He did allow that PAG costs make it unlikely that many consumers would use that type of engine oil for replacement fill. That doesnt bother OEMs, he said, because the penalties tied to CO2 limits apply to new vehicles.