Times are Changing!


APISNPlusMOBottleThe Petroleum Quality Institute of America (PQIA) has been analyzing engine oil samples since 2009. Over that time, we have tested many brands, the majority of which have no issues; they meet their viscosity claims and are consistent with the API Service Categories on the labels. Unfortunately, however, we have also seen a significant number of brands with deficiencies, and some that are so far off the mark they will cause harm to engines. While PQIA will continue to inform consumers about motor oils that have no issues, and those that fail to meet their claims and/or can cause equipment harm, this article is written to help educate consumers about an important change taking place in motor oils they should be aware of. This change speaks to the new API SN Plus Service Category for passenger car motor oils (PCMO) and how it will likely be seen in the sample analysis data PQIA reports.

The Trends and Changes

In addition to help sort out the good from the bad in motor oils, the PQIA reports provide a significant body of data with regards to the chemical makeup, or as some call it, the chemical profiles or signatures of the various lubricants we examine. As one would expect, there are many similarities and differences in the chemical profiles and what can be gleaned from them. But with API SN Plus about to commence, times are changing. So rather than leaving our readers scratching their heads and wondering about differences in the additive levels they will likely see in the samples we test, PQIA would like to bring these changes to the attention of our readers as they develop.

As shown in the table below, although API SN Plus first licensing date is May 1, 2018, we have already noticed a spike in the level of magnesium in samples tested year-to-date (YTD). The average magnesium level in the products tested so far in 2018 is 240 ppm, up from 10 ppm in 2016 and 2017. This would indicate a change in detergent chemistry for API SN Plus has already been made in some of the brands tested.


In addition to an increase in magnesium, we also see changes in the levels of calcium.

Historically, we have seen calcium as the primary element for detergents or calcium together with sodium. Few passenger car motor oils tested were using any significant levels of magnesium detergents. With the rise in magnesium already seen in 2018 we have also observed declines in calcium and what appears to be a drop in the sodium.

Another trend we are seeing is that the total base number (TBN), which is driven primarily by the detergent additive, is inching up. It has reached an average of 7.8 in the samples tested in 2018, up from 7.4 and 7.5 in 2016 and 2017, respectively.

While it is too soon to draw conclusions about these developments, the PQIA test data suggests that the chemistry for API SN Plus is already making an impact.

Elements3The changes PQIA is observing to the organometallic additives in the samples tested in 2018 come as no surprise. The published literature and comments about the new Ford and GM tests for low speed pre-ignition (LSPI) indicate additive technology impacts the new test and calcium can contribute to LSPI. With that, it appears magnesium is emerging as a remedy for LSPI.

The zinc dialkyldithiophosphate (ZDDP) levels have remained relatively stable over the past three years and this is not expected to change. This is because the phosphorus for nearly all PCMO viscosity grades has a minimum and maximum chemical limit of 600-800 ppm for API SN and SN Plus. Since the level of zinc in the ZDDP molecules are stoichiometrically tied to the phosphorus, unless the specification for phosphorus changes, it is unlikely we will see any significant changes in phosphorus or zinc levels in the API SN Plus samples PQIA examines.

Another observation from the samples tested is a decline in the level of boron and an increase in molybdenum. Whereas it too soon to determine if this is a trend, more will be learned as PQIA’s sample set of data grows in 2018.

PQIA will keep you posted on these and other trends observed as API SN Plus rolls out.

Note: It’s important to keep in mind that additive companies and marketers always look to optimize and improve their lubricant chemistry, so not all changes are likely due to LSPI alone. It is also important to note that in addition to changes seen in the PQIA test data related to API SN Plus, other changes and improvements are likely in additive (and base oil) chemistries that will not be seen in the slate of tests PQIA conducts to assess motor oil quality. Readers are reminded to take this into consideration before comparing one product to another, and that although PQIA’s slate of tests alone cannot be used to establish if engine oil meets an API Service Category, they can be used to determine if it doesn’t.


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