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Low-speed pre-ignition (LSPI): 4 things you should know

Unsurpassed LSPI protection

Today’s engines are smaller, more efficient, more advanced and more powerful. But those engines, especially turbocharged gasoline direct-injection (TGDI) engines, also create extreme operating conditions, which make them more susceptible to something called LSPI.

1. LSPI can damage your turbocharged engine. But Mobil 1™ motor oils can help prevent engine damage by providing outstanding LSPI protection.

LSPI creates excessive pressure within the engine’s cylinders, which can cause permanent damage to cylinder walls, pistons, piston rings, connecting rods and spark plugs. The internal engine damage caused by LSPI can also lead to catastrophic engine failure.


Outstanding LSPI protection: Mobil 1™ motor oil
Mobil 1™ preventing LSPI

Mobil 1™ 5W-30 advanced full synthetic motor oil was tested against a competitive full synthetic oil in some of the toughest conditions. Engines of Las Vegas taxis were pushed to their limits, running 24 hours a day in extreme temperatures and stop-and-go traffic.


2. LSPI involves abnormal combustion.

LSPI is not something your engine was designed to do. LSPI or “super knock” is an abnormal combustion event that can occur in TGDI engines. This event can take place when the air-fuel mixture ignites before the spark plug fires.

LSPI typically occurs when an engine is under high load at low rpm (i.e., driving slowly and then rapidly accelerating). LSPI is caused by particles or droplets of fuel and oil that ignite in the combustion chamber. Unlike the engine knocking sound associated with bad spark plugs, ignition timing issues or by using the wrong type of fuel, LSPI is known to create a distinctively loud bang.


Inside the engine: LSPI vs. Normal combustion
LSPI infographic

Internal combustion engines depend on precise spark timing to maximize power and efficiency. Spark-triggered ignition is designed to work in tandem with the pistons, creating pressure through combustion to support the pistons’ downward movement. If ignition occurs too early, then the pressure clashes with the upward movement of the pistons.

SN Plus API Service

3. API SN Plus was developed to help prevent LSPI.

API SN Plus is a supplemental oil category from the American Petroleum Institute (API). The oil formulations for API SN Plus are specifically designed to help prevent LSPI in TGDI engines. API SN Plus represents an improvement on API SN, an oil category developed in 2010.

May 1, 2018 is the first licensing date for API SN Plus. The API SN Plus donut symbol will start appearing on Mobil™-branded motor oil labels (the back of the bottles) throughout 2018.


4. Mobil 1 motor oils are so advanced that they have met the API SN Plus performance standard since 2010.

Many Mobil 1 motor oils already meet the API SN Plus performance standard, making these full synthetic oils more than seven years ahead of their time for providing protection against LSPI.

Mobil 1™ motor oil variations

The following motor oils fulfill the API SN Plus specification:

These motor oils can be purchased now, but the current packaging won’t feature the API SN Plus donut symbol. The donut symbol will start appearing on our products throughout 2018.


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