Off-the-shelf samples of SAE 0W-20 and 5W-30 engine oils in Asia have been found to generate higher levels of phosphorus emissions than their counterparts in the Americas, according to a United States-based testing company.
Phosphorus levels in emissions are of interest because they can compromise systems designed to reduce the release of pollutants. In a presentation at the Society of Tribologists and Lubrication Engineers Annual Meeting and Exhibition on May 20, The Institute of Materials Operations Manager Tina Dasbach noted that phosphorus emissions levels for both 5W-30 and 0W-20 oils fell significantly in Asia and the Americas from 2009 through 2012, based on testing of oil samples collected by IOM.
But she also noted that phosphorus levels – measured by a phosphorus emissions index – leveled off during the past three years. She suggested that this may be cause for concern, especially in Asia.
The importance of phosphorus and exhaust emissions will continue to be a challenge moving forward, particularly as has been shown in large Asian cities, Dasbach said. STLEs meeting was held in Dallas, Texas, United States.
Part of The Savant Group, Midland, Mich.-based The Institute of Materials provides data on the physical, chemical and performance-associated characteristics of automotive oils obtained from the worldwide marketplace. Each year, IOM collects 650 samples of light- and heavy-duty engine oil from retailers around the world – 250 in the U.S., Canada, Mexico and South America; 250 from Asia-Pacific; and 150 from Europe. The institute has collected and analyzed over 14,000 engine oil samples since its inception.
In addition to phosphorus emissions index levels, Dasbach compared results between Asia and the Americas for engine oil volatility and viscosity characteristics. Engine oil volatility is a problem for vehicle owners because it contributes to oil degradation and engine contamination. It also contributes to emission of pollutants. IOM tested oils using ASTM Internationals Noack volatility test (ASTM D5800), which determines the evaporation loss of a lubricant as percentage weight loss under specified test conditions.
Dasbach noted that conventional oils tend to vaporize more than synthetics and that the lightest oil fractions evaporate first. 0W-20 oils from the Americas had lower volatility than their Asian counterparts, but 5W-30 oils from Asia tested better than those from the Americas. Dasbach noted that all of the 5W-30 and 0W-20 engine oil averages fall below the 15 percent limit prescribed by specifications. Still, she advised that volatility warrants attention because of the industrys shift toward lighter oils as it tries to help automakers improve fuel economy.
However, with the oncoming lower viscosity engine oils such as SAE 0W-16 and lower, there will certainly be a volatility challenge, she said.
IOM found that high-temperature/high-shear viscosity of Asian 0W-20 oils has decreased since 2009, from approximately 5.5 centiPoise to about 5.2 cP last year. HTHS rates of 0W-20 oils in the Americas remained in the range of 5.6 cP during that time. Oils from both regions have shown an ability to retain their HTHS rates during use, so the decline in viscosity for Asian oils is not a cause for concern, Dasbach said. She speculated that it may be part of the broader push by Asian companies toward lower viscosity.