How to avoid Low Speed Pre-Ignition 

January 03, 2024
How to avoid Low Speed Pre-Ignition 

LIQUI MOLY has issued some useful advice on how to avoid the problem of Low Speed Pre-Ignition. 

The term “Low Speed Pre Ignition” (LSPI) refers to the pre-ignition phenomenon in the engine. It describes an undesired combustion before the planned ignition. The premature explosion in the combustion chamber, counteracts the natural piston movement. This can lead to engine knocking and thus to serious engine damage. 

In many cases, LSPI is noticeable in the form of minor explosions, which lead to jerking in the engine before major engine damage and damage such as a broken cylinder head gasket, worn piston rings or a defective connecting rod bearing shell. 

The problem of premature ignition at low engine speeds only exists in modern, high-compression engines with direct injection, which operate in the low engine speed range and under high load. The reason for this is the functional design of these engines, which are designed for maximum power output in such a way that combustion inside the engine, must take place faster and hotter than with conventional engines. As a result, the fuel only evaporates for a short time, which causes the risk of droplet formation, which can lead to unclean or incomplete combustion due to afterglow.

Driving at low revs and a cold engine promotes this pre-ignition. However, using the wrong motor oil can also lead to LSPI. This is because engines with direct injection require low-viscosity oils. These enter the combustion chamber more easily to form the explosive mixture for the required faster and hotter combustion processes. Due to the short time window of an explosion, this process must work smoothly and without complications to prevent extraordinary explosions.

Avoiding driving at low revs when cold is one way to prevent LSPI, but this is not always possible. LIQUI MOLY therefore recommend the use of special motor oils that prevent pre-ignition, such as oils from he Special Tec AA range as well as Special Tec DX1. As part of the API SN Plus+RC specification, these are subjected to an additional LSPI testing.

For example Special Tec DX1 is a high-tech low-friction motor oil based on synthetic technology. It optimises fuel consumption, ensures excellent cold-starting characteristics, optimum wear protection and excellent engine cleanliness. The innovative additive technology minimizes LSPI and thus ensures a longer engine service life. In addition, it is ideally suited for long oil change intervals and high engine requirements.

It was developed specifically for the requirements of GM and Opel vehicles with petrol engines. However, it is also often used in different types of vehicle manufactured by Chrysler, Ford, Kia, Honda, Hyundai, Mazda, Nissan, Toyota and more, which require this specification. 

The Special Tec AA motor oils are most suitable for modern Asian and American petrol engines. They are particularly suited to long oil change intervals and high engine demands. These oils also offer a reduction of Low Speed Pre-Ignition, save fuel and reduce emission. The range covers AA 0W-08, AA 0W-16, AA 0W-20, AA 5W-20 and AA 5W-30. 

These oils are available from LIQUI MOLY stockists nationwide. 

More information can be found in the video below. 

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