To assure that they can use lighter-vis oils without fear of excessive engine wear, some automakers have asked SAE for an expanded set of the regular grades, adding SAE 5, 10 and 15. The big issue – and one that the OEMs themselves don’t agree on – is how and where to set the high-temperature/high-shear viscosity limits for these new grades. The lowest HTHS viscosity allowed today is 2.6 mPa.s-sec, at 150 degrees C, and some proposals would take this much lower.

Task Force Chairman Chris May of Imperial Oil opened the June 22 meeting in Baltimore with a review of the drivers for these additional grades. Since August 2009, a working group has been assessing the options for extending SAE J300 viscosity grades to oils with HTHS below 2.6 mPa.s.

Last summer, industry stakeholders were polled regarding three options under consideration. Some respondents to the poll advised caution in making any changes to J300 until needs and implications were better defined, May said. Others pointed out that there are already low-viscosity products in the marketplace claiming to meet “SAE 0W-10” (including one marketed by a Japanese OEM) and “10W-10 grades that don’t exist. This brings urgency for an SAE definition of these new grades.

The proponents for changing SAE J300 generally fell into two groups, May reported: those who advocate adding a full slate of viscosity grades below SAE 20 (down to 1.4 mPa.s), and those who want to add only one or perhaps two new grades below SAE 20. J300 can be revisited to add additional viscosity grades, the latter point out.

Most respondents to the poll agreed that any new grades should have distinct kinematic viscosity ranges as well as HTHS limits; this would also affect SAE 20 grade definitions. Most also appeared comfortable with HTHS increments of 0.3 mPa.s for each new grade, May said.

Jeff Jetter from Honda said his company plans to use lower-viscosity oils, and sees the use of such oils as helping to develop new engine technologies. He said this also is potentially the last change in J300 due to the “electrification” of internal combustion engines. Honda wants to capture every bit of technical advantage through the use of low-viscosity engine oils.

While not offering specific limits, Jetter proposed there should be four new viscosity grades, with a twist: Instead of HTHS overlap and no KV overlap, as is the current case, HTHS viscosity would not overlap and KV would. Honda believe that with this system, each OEM can choose the optimum oil for its engines.

Sliding wear is the most critical issue facing Honda and its engines, Jetter added. He provided data showing that the lightest oil (referred to as “Category 5”) gave satisfactory antiwear performance in current production engines. While Honda is satisfied with the protection offered, “Category 5” oils will not be applied to existing engines, Jetter said, because some components rely on oil pressure to function. However, future engine designs can be optimized to operate with this oil, he added.

Minoru Yamashita reported that Toyota wanted to see a change in SAE 20 grade to a higher minimum viscosity and that a new grade be introduced which had a lower KV range as well as a lower HTHS minimum. The new viscosity grade could result in fuel economy improvements of up to 0.7 percent due solely to viscosity, according to Toyota.

Ron Romano of Ford Motor noted that it would be important to manage the spread in kinematic viscosity limits, as it affects hydraulic specifications, and engine oils are also expected to perform some hydraulic functions in automotive engines. While the test measurements are carried out over a narrow temperature range, the actual calibration of hydraulics is over a much greater range of temperatures. Tracey King of Chrysler concurred with Romano in this assessment.

Isabella Goldmints of Infineum offered data on a series of blended oils using API Group III and Group IV (polyalphaolefin) base stocks. She said the results showed it’s possible to blend oils with HTHS viscosity down to about 1.5 mPa.s, but at the expense of higher volatility.

Mike Covitch and Gail Evans of Lubrizol offered data and a proposal to split viscosity grades: essentially a “high” and “low” range for each grade. They cautioned that it was important to define HTHS limits while also defining kinematic viscosity ranges that are needed for consistent hydraulic performance and which can be practically manufactured.

Many in the industry have expressed concerns about how these new, lower viscosity oils will be identified. Getting the nomenclature part of the definition right is critical they say, and using SAE ‘5’, ’10’, or ’15’ has the potential for consumer confusion and misapplication. It may require a significant departure from the designations which have been used for almost 100 years.