Industry Tackles GF-5 Fuel Economy Definition


DETROIT – Fuel economy in GF-5 is not locked in concrete yet and is still debatable, said Afton Chemicals Dewey Szemenyeiof an Open Forum at SAEs Fuelsand Lubricants Council here April 12. Industry experts aired proposals at the forum for altering SAE J-300, theindustry standard that is used for classifying engine oil viscosity, to address fuel economy requirements for the next passenger car engine oil specification.

General Motors Mike McMillan and Savants Ted Selby coauthored a proposal for an alternative system to J-300, an Oil Classification Triangle.

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SAE J-300, Engine Oil Viscosity Classification, is the primarydocument used by the lubricant industry to define an engine oils thickness and ability to flow at certain temperatures.

While J-300 has been in use many years, it is rigid. Consumers dont understand it, its difficult to modify to incorporate technical advances in high quality base oils, and its awkward grading system makes it difficult to include the influence of engine oil viscosity on fuel efficiency, McMillan said.

Since J-300 is based on earlier understandings and needs, it doesnt fit with new technical opportunities. While much effort has been invested in seeking ways to modify this standard, they have not been successful, McMillan continued. However, replacing or drastically modifying J-300 is problematic since it is used in many specifications other than engine oil.

Because J-300 is not likely to go away or be greatly modified, McMillan and Selby proposed that an alternative, consumer-friendly, open-to-progress system be established, one capable of incorporating modern developments for higher performance and fuel-efficient engine oils. The alternative system would be easily understood by non-technical users, self-consistent and simple to apply, easily extendable to any new technology and based on meaningful bench tests.

Oil Classification Triangle:

Schematically, their proposed alternativesystem came in the form of a triangle approach in order to classify engine oils according to three areas of importance:

In the illustration above, the +8 fuel efficiency classification value means 0.8 percent improvement over the reference oil. The high shear rate classification value of 3.0 means that the oil viscosity at operating temperature is within 3.0 to 3.5 centipoise at 150 degrees C. And the low temperature classification value is the lowest temperature at which the oil should be used.

A low temperature classification value of G: -30 means that gasoline engines will start and the oil will pump at minus 30 degrees C. For the same oil in a diesel engine, D: -20 means that diesel engines will start and the oil will pump at minus 20 degrees C. Other operating temperatures could be used for the viscosity value and determination of fuel efficiency.

For their proposed alternative system, McMillan and Selby noted that bench test tools are already available. Finally, they emphasized that, for reasons noted above, their new system is an alternative to, not a replacement, for J-300.

Extending J-300
A second presentation also focused on ways to make SAE J-300 more responsive to current needs and issues. Andrew Jackson of ExxonMobil Researchand Engineering presented a paper coauthored with his ExxonMobil colleagues Doug Deckman and Charles Baker and Imperial Oils Chris May.

Jackson focused on the need to extend SAE J-300 to include low viscosity, high viscosity index (V.I.) oils that can give high fuel economy.

Jacksons highly technical proposal noted, SAE J-300 does not contain the necessary low viscosity grades. Testing shows that there is a clear fuel economy benefit from the use of low viscosity, high V.I. oils, yet the only classification that SAE J-300 gives them is 0W, which is inadequate and aesthetically unappealing to consumers. Further, the 0W-xx grades assigned to current fuel efficient, low viscosity, high V.I. oils have led to confusion in the marketplace.

Jackson presented schematic data to show both the fuel economy innovation area and the inadequate coverage in high temperature/high shear (HTHS), kinematic viscosity and W grades.

To address the inadequacies in SAE J-300, while at the same time leaving the majority of the standard intact, Jackson compared SAE J-300 to the International Standards Organization’s viscosity grades. The ISO standard indicates that four new viscosity grades could be added to J-300, possibly splitting current SAE 20 into two grades, 15 and 20, then adding 10 and 5, setting kinematic viscosity limits by logarithmic separation, as is done by ISO, and then projecting to corresponding HTHS limits.

Jackson continued with a proposal to modify the description ofSAE J-300’sW grades. Cold-start temperatures could be added to 5W, 10W, etc., which would continue to ensure cold starting and oil pumpability but use nomenclature that the customer could understand. The next step would be to develop a better way to describe sub-5W grades than calling them 0W.

Jackson noted that high fuel economy oils do not need to meetcold cranking simulatorandmini-rotary viscometerlimits at lower temperatures than currently used for 0W. Instead, a way is needed to characterize the dynamic viscosity-temperature profile at medium to high shear rates and low to medium temperatures (20 to 80 degrees C).

Summing up his proposal, Jackson said, Following these changes, in five years it might be possible to drop kinematic viscosity and use HTHS only for SAE grades, to drop the W grade name and use temperature only, and to include the important viscosity effect on fuel economy through the addition of a moderate temperature, moderate shear rate dynamic viscosity.

Other Voices
In addition,the open forum heard presentationsby Chevron Oronites Alex Boffa on fuel economy modeling; Infineums Andy Richie on his companys perspective on GF-5 fuel economy; GMs Mike McMillan on the need for field correlation; Fords Ron Jensen on opportunities for fuel economy improvements from lower viscosity oils; and Lubrizols Brent Dohner on the tradeoff between fuel economy and durability.

Afton Chemicals Dick Kuhlman and Dewey Szemenyei chairSAE’s two lubricant-relatedTechnical Committees onengine lubrication andon drivelineand chassis. These two essential committees are responsible for maintaining all of the SAE J documents, a total of 24 industry standards. J-300, Engine Oil Viscosity Classification, for example, is the primary, worldwide standard for classifying viscosity.

Recognizing that open forums are a wellregarded method to strengthen the committee structure, Kuhlman and Szemenyei selected two important issues for last week’s meeting: 1)How should GF-5 fuel economy be defined? and 2) Unlicensed motor oils in the marketplace. See next week’s issue for a report on the unlicensed-oil forum.

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