OEMs have been aggressively downsizing engines to meet strict fuel economy and emissions standards while improving power and torque. Most new engines today use some combination of turbochargers, direct-fuel injection and variable valve timing to make more power than their larger counterparts while delivering improved fuel economy. This scenario seems like all upside for drivers. But today’s smaller, hotter-running engines pose significant challenges to lubricants. The latest is a phenomenon called low-speed pre-ignition (LSPI), also known as “super knock,” which can destroy pistons and connecting rods.
What Is LSPI?
LSPI is another version of engine knock, which has been around since engines were invented. In this case, it occurs under low-speed, high-torque conditions in turbocharged gasoline direct-injected engines – like when you’re taking off from a stoplight. LSPI is the spontaneous ignition of the fuel/air mixture prior to spark-triggered ignition. This form of pre-ignition is more destructive than typical engine knock.
No Magic Bullet
Just as your engine relies on a balanced network of components to function, the motor oil needed to protect it requires additives with the right qualities at the right quantities. While adding more of one ingredient or reducing another seems simple enough, small composition changes can have big impacts. We were determined to find a solution to the LSPI problem without sacrificing the performance of Signature Series in any way.
GM SPI Test
OEMs like GM have addressed the issue by designing tests to determine a motor oil’s ability to prevent LSPI. The GM SPI Test records the number of peak pressure events during high-load
operation in a turbocharged engine over a five-hour period. Passing the test is required to meet the GM dexos1® Gen 2 specification.
Engine GM 2.0L EcoTec, LHU
Duration Five hours
Measures Number of peak pressure pre-ignition events
Simulates Turbocharged vehicle operating in high torque and at low speed
Requirement At least three of the five total tests with zero peak pressure LSPI
events and no tests with more than two peak pressure events
We armed Signature Series with an advanced detergent system that protects against harmful deposits and LSPI. Signature Series Motor Oilachieved 100 percent protectionagainst LSPI in the engine test required by the GM dexos1 Gen 2 specification – zero occurrences were recorded throughout five consecutive tests.
API SN PLUS Specification
API SN PLUS is a recently released specification that was requested by the automobile industry to protect passenger vehicles from LSPI. AMSOIL anticipated this change, and the current
formulations of Signature Series, XL and OE synthetic motor oil all meet or exceed the specification. Look for updated product labels featuring the new API “donut” in the near future. You can be confident that AMSOIL synthetic motor oils protect modern engines against LSPI, helping your vehicle deliver years of reliable service.
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