Correct Combustion Cycle
To maintain optimal performance, the engine must not be started until after the air/fuel mixture has been compressed in the cylinder and the piston has started to move upwards. In that moment, the spark occurs, the fuel is burnt and pushes the piston, adding power to the engine.
Premature detonation occurs when the fuel is burnt before the spark takes place. In this instance, power generated by the detonation works against the engines power, a “ping” sound is heard and it can cause severe damage to the engine.
Rattle in the engine
In mechanic slang, this term indicates that premature detonation is happening.
What happens if I use lower octane gasoline?
Using gasoline with lower than recommended octane levels will decrease its overall performance and might even lead to premature detonation which can damage the engine.
The impact of dirty fuel injectors
Deposits found in the injectors can result in the fuel not being properly dispersed. It is not turned to mist, being that the drops of fuel are not as small as they should be. This leads to an incomplete fuel combustion which in turn decreases the overall performance of the engine and contributes to a higher level of emisions being cast out to the environment. Additionally, it accelerates the formation of more deposits. It´s a vicious cycle.
Furthermore, the deposits inside the injectors will block the fuel from entering the combustion cylinder. This in turn makes it necessary for more power to be exerted in order to inject the same amount of fuel as before. As the engine is using more and more of the injection pressure available to overcome the blocking of the injectors, the engine doesn´t respond as fast as it did before, it can lose acceleration capacity and not be able to reach the maximum potential it was designed to reach.
The impact of dirty valves
The deposits found in the valves can restrict the amount of air, or air/fuel mixture, that enters the cylinder. Correspondingly, it can limit the amount of combustion gases that get out.
It can cause the valves to not seal correctly, leading to exhaust gases entering the fuel supply system, or it can cause the air and fuel mix to leak without having been burnt.
It can cause a valve to get jammed and not be able to open when it needs to. If no fuel is supplied to that cylinder, the engine will lose significant power and performace.
The impact of fuel deposits in the piston or the cylinder itself
Deposits found on the head of the piston or on the combustion cylinder occupy space and may change the engine´s compression index. This alteration the compression index may lead to premature detonation, which in turn would lead to the engine needing higher octane gasoline to avoid engine knocking.