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Oak Ridge-GM prototype low-viscosity ionic liquid-additized engine oil delivers 2% fuel economy improvement over 5W-30

30 December 2013

A team from Oak Ridge National Laboratory and General Motors, led by ORNL researcher Dr. Jun Qu, has developed a new group of ionic liquids as lubricant additives that could help improve the energy efficiency of cars and trucks. Prototype low-viscosity ionic liquid-additized engine oil demonstrated a 2% improved fuel economy compared to Mobil 1 5W-30 engine oil (3.93% over the 20W-30 baseline oil) in standard fuel efficiency engine dynamometer tests. The prototype oil also successfully passed a 100-hour high-temperature, high-load engine dynamometer test.

Friction is the cause of the loss of ~10-15% of the energy in an internal combustion engine; for the transportation sector, parasitic friction (primarily induced by elastohydrodynamic drag between the piston rings and cylinder liners, which is proportional to the lubricant viscosity) consumes approximately 400 million barrels of oil annually in the US. Accordingly, the US Department of Energy’s (DOE’s) Vehicle Technologies Office, which sponsored this research, has set a goal of 2% fuel economy improvement via lubricant advances by 2015.

This breakthrough ionic lubricant technology could potentially save the US tens of million barrels of oil annually.

—Dr. Jun Qu

Ionic liquids are “room temperature molten salts”, composed of cations & anions, instead of neutral molecules. In a 2012 paper published in the journal ACS Applied Materials and Interfaces, Qu and his colleagues noted that:

Ionic liquids [ILs] have been explored for lubrication applications since 2001. The majority of the literature has focused on using ILs as neat lubricants or base stocks, which would be suitable for special bearing applications such as for operation at >250 °C where conventional hydrocarbon lubricants start decomposing, but many ILs are stable. Another approach is to use ILs as lubricant additives, which has significant practical merit because it may get into the lubricant market without requiring major supply and distribution changes. However, most ILs have little or no solubility (≪1%) in nonpolar hydrocarbon oils. Most previous studies used unstable oil-IL emulsions or low concentrations of ILs in nonpolar base oils, and others used a polar base stock for better compatibility with ILs. Therefore, there is a significant opportunity for developing ILs with good solubility in nonpolar lubricating base oils.

In this paper, we report the results of research on the IL trihexyltetradecylphosphonium bis(2-ethylhexyl) phosphate, which is not only soluble but fully miscible in common non-polar hydrocarbon oils. Results with this IL reported here have demonstrated high thermal stability, noncorrosiveness, and high effectiveness in reducing friction and wear when blended into lubricating oils. Surface boundary film examination revealed the antiwear mechanism for the IL additive and its synergistic effects with an existing additive package.

—Qu et al.

In general, they noted, ions and non-polar neutral organic molecules are immiscible, because ions are attracted by polar forces, whereas non-polar molecules are held together by dispersion forces. They hypothesized that the exceptional oil-miscibility of their ionic liquid is due to its three-dimensional quaternary structures with high steric hindrance (long hydrocarbon chains) that dilute the charge of the ions and therefore improve the compatibility with neutral oil molecules.

In contrast, most ILs that have been studied contain either two-dimensional cations or small anions, and thus cannot dissolve in oils. Their experiments also found that, in addition to the quaternary structures, an oil-miscible IL needs to contain at least one alkyl with four carbons or more for both the cation and the anion.

In a newer paper in Tribology International, the team reports the anti-scuffing/anti-wear behavior and mechanism of the oil-miscible ionic liquid in a base oil at 1.0 wt% concentration under both room and elevated temperatures. Results are benchmarked against those for a conventional anti-wear additive, zinc dialkyl-dithiophosphate (ZDDP).

They conducted reciprocating sliding, boundary lubrication tests using a piston ring segment against a cylinder liner piece cut from actual automotive engine components. Although the IL and ZDDP worked equally well to prevent scuffing and reduce wear in the room-temperature tests, the IL significantly outperformed ZDDP in the 100 °C tests.

Furthermore, they found that ionic liquid additives have potentially less adverse impact on TWC (three-way catalysts) compared to ZDDP.

Further development and optimization of IL molecular structures and lubricant formulation are being conducted.

Resources

  • Jun Qu, Dinesh G. Bansal, Bo Yu, Jane Y. Howe, Huimin Luo, Sheng Dai, Huaqing Li, Peter J. Blau, Bruce G. Bunting, Gregory Mordukhovich, and Donald J. Smolenski (2012) “Antiwear Performance and Mechanism of an Oil-Miscible Ionic Liquid as a Lubricant Additive,” ACS Applied Materials & Interfaces 4 (2), 997-1002 doi: 10.1021/am201646k

  • Jun Qu, Huimin Luo, Miaofang Chi, Cheng Ma, Peter J. Blau, Sheng Dai, Michael B. Viola (2014) “Comparison of an oil-miscible ionic liquid and ZDDP as a lubricant anti-wear additive,” Tribology International, Volume 71, Pages 88-97 doi: 10.1016/j.triboint.2013.11.010

December 30, 2013 in Fuel Efficiency, Lubricating Oils | Permalink | Comments (4) | TrackBack (0)

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Comments

Im very interrested to get this on my next engine oil purchase and save 2% of regular gasoline. Actually i have a dodge neon 2005 and i put 5w30 conventional engine oil instead of synthetic because it is cheaper and also synthetic have a tendacy to wear the engine gaskets. My manual specify 5w20 but i prefer 5w30 to save the engine on the long run.

When i was young i purchased all kind of oil additive like tufoil and some others too and i had leak problems. Does this additive is hard on gaskets and provoke leaks ?? They should inquire.

The best way to save on fuel is to accelerate slowly and reduce speed to just below traffic speed when possible and coast to stops. With a manual transmission like mine it is easier, i also do short shifts to keep rpm low. I often get to a steep downhill with a stop at the bottom and i compress the engine which take gas but it help the breaks, this is the only compromise i do.

Gorr...coasting to every stops is even easier with a Toyota Hybrid. It is one way to save more gas.

I use the recommended Toyota's 0-20 synthetic (actual Mobil 1 Synthetic oil).

Wouldn't mind using this additive if it doesn't affect the Toyota warranty. Will try to get confirmation when the additive becomes available and if it is affordable.

Gorr,

Every bearing and tolerance in your engine was designed for synthetic 5w20. If you are using conventional 5w30, you are throwing money out the window. Not only are you wasting extra fuel pushing that needlessly thick goop around (and that goes double this time of year), you are also shortening the life of your engine by using an inferior product. Stick to what your manual tells you and you will be a happier, richer man. As the article above shows, oil can make a big difference in fuel economy, and your choice of cheap, wrong-grade dino oil is likely costing you a litre or two per tank (2-4%). You do the math.

The good news is that your habit of using engine braking isn't using any more gasoline. If it was, you would be accelerating (or at least keeping a steady speed). One of the side benefits is that engine braking creates a vacuum in the combustion chambers that can suck a little bit of oil past the piston rings, providing additional lubrication.

BTW, that old mechanic's tale about synthetics being bad for seals hasn't been true in 40 years. All modern cars are designed to use synthetics. Dinosaur oils will cause extra wear and sludge, which means junking your car sooner. That's good for the car companies, but bad for you.

Ok . i will try synthetic 5w20. I just remember that i have a friend that has a corrolla 1998 run with synthetic and he do not have leak.

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