随着如今使用直喷技术的汽油车越来越多，低速早燃（LSPI）问题也逐渐被人们所关注。它是一种汽油直喷发动机特有的问题，是在火花塞点火之前发生的一种预料之外的汽油自燃现象，如果连续发生，很可能导致发动机故障。
当代四冲程汽油发动机具有“吸压爆排”四个冲程，在吸气冲程时，直喷系统的高压喷油嘴会将雾化的汽油斜向喷射到其对面的气缸壁上。这些雾化的汽油本应该静静等待被火花塞点燃，然而事与愿违，其中一部分汽油与气缸壁的机油膜发生了结合，液化后形成了汽油机油混合物。在接下来的压缩冲程里，这些混合物又被上行的活塞刮成了液滴，随着活塞逐渐靠近上止点，燃烧室内也会逐渐形成让汽油机油混合物自燃的高温高压条件。最终，汽油机油混合物在火花塞点火前发生了自燃和爆炸，这就是“低速早燃”。
低速早燃发生后，剩下的油气混合气紧接着按正常流程被火花塞点燃，这样一下一上的两个爆炸，使活塞承受了更大的压力，发动机从而也会出现伴随金属敲击声的“爆震”现象。长此以往，不堪重负的活塞会逐渐产生裂缝，甚至会断裂，并对发动机造成严重损害。
为了应对低速早燃，众多润滑油厂商已经纷纷研发出了新的机油配方，其可以从源头避免雾化的汽油与机油发生反应和自燃，从而实现从源头避免低速早燃发生的功能。如果您爱车的发动机采用直喷技术，且您在日常用车的过程中经常遇到发动机爆震的话，在选择机油时，可以更多留意带有应对低速早燃配方的产品。
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With the increasing number of petrol vehicles using direct injection technology today, the problem of Low Speed Early Ignition (LSPI) is becoming a growing concern. It is a problem specific to direct injection petrol engines and is an unanticipated spontaneous ignition of petrol that occurs before the spark plugs ignite and, if it occurs continuously, is likely to lead to engine failure.
Contemporary four-stroke petrol engines have four strokes of "suction and pressure", and during the suction stroke, the high pressure injector of the direct injection system will spray the atomised petrol diagonally to the opposite cylinder wall. The atomised petrol should have been waiting for the spark plug to ignite, but instead, some of the petrol combines with the oil film on the cylinder wall and liquefies to form a petrol-oil mixture. During the next compression stroke, this mixture is scraped into droplets by the upward moving piston, and as the piston moves closer to the upper stop, the combustion chamber gradually develops the high temperature and pressure conditions for the gasoline oil mixture to ignite spontaneously. Eventually, the oil mixture spontaneously ignites and explodes before the spark plug ignites, which is known as "low-speed premature ignition".
After the early low-speed ignition occurs, the remaining oil and gas mixture is then ignited by the spark plug according to the normal process, so that the two explosions at once, so that the piston is subjected to greater pressure, the engine will also appear with the metal knocking "popping" phenomenon. In the long run, the overburdened piston will gradually crack or even break and cause serious damage to the engine.
To combat low-speed premature combustion, many lubricant manufacturers have developed new oil formulations that prevent atomised petrol reacting with the oil and spontaneous combustion from the source, thus preventing low-speed premature combustion at source. If your car's engine uses direct injection technology and you experience frequent engine bursts in the course of your daily use, you may wish to pay more attention to products with formulations to combat low-speed premature ignition when choosing your oil.
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