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Why have the zinc/phosphorus levels in motor oil changed?

April 26, 2017changed levels motor Oil Phosphorus zinc

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Why have the zinc/phosphorus levels in motor oil changed?

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With ever increasing limits on emissions, automobile manufacturers have tightened emission control systems on newer vehicles. This is one of several factors considered when the American Petroleum Institute (API) sets standards for motor oil. The current API standard is “SM” which replaced the previous “SL” classification. Because phosphorus can poison a vehicle’s emission system, the level of zinc is lower for current motor oil.