The recently introduced API SP Service Category and ILSAC GF-6A/6B standards complete the process to upgrade passenger car motor oils. The process started with changes introduced for API SN Plus to mitigate low-speed pre ignition (LSPI) in the rapidly growing population of turbocharged, direct-injected (DI) gasoline engines. LSPI events can cause engine knocking, decreased efficiency, and in the worst case catastrophic failure due to cracked pistons.
As with API SN Plus (see related article below), the motor oils PQIA tested meeting the new specifications are formulated with lower calcium and higher magnesium levels than motor oils meeting API SN and earlier specifications. Although calcium had been favored for decades, industry research has shown fewer incidents of LSPI occurring when the detergent chemistries are rebalanced to reduce the level of calcium and increase the level of magnesium in the additive package. Calcium has been shown to promote LSPI, while magnesium has little to no impact.
Based on nine API SP/ILSAC GF-6A licensed brands of motor oil recently examined by PQIA, the following chart provides early statistics on the levels of organometallic additives and Total Base Number for motor oils meeting the new specifications.
It is important to note that there will likely be products in the market where the elemental analysis and TBNs fall outside of these ranges and the motor oils still meet the new specifications. The chart provides only a sense of what we can expect to see and it would be inappropriate to draw inferences about the performance of an API SP ILSAC GF-6A motor oil based solely on the level of individual organometallic elements from the additives in a formulation.
