There are several reasons why oil-burning engines are more susceptible to knocking:
First of all, the oil contains a lot of additives and anti-wear agents, which can improve the lubricating properties and anti-wear properties of the oil. However, when the oil burns, these additives and anti-wear agents can remain inside the engine, forming carbon deposits and sludge. These carbon deposits and sludge can clog piston rings and injectors, resulting in uneven fuel injection, localized overheating and knocking.
Secondly, the combustion of engine oil produces a large amount of water vapor and acidic substances, which can corrode the metal surface inside the engine, causing metal spalling and localized high temperatures. These metal particles and high temperatures can further exacerbate uneven fuel injection and localized overheating, which can cause knocking.
In addition, oil-burning engines often experience insufficient cylinder pressure. When the piston rings are worn or stuck, it can cause the cylinder to be poorly sealed, allowing oil to enter the combustion chamber. At the same time, the seizure of the piston rings can also affect the flow of gas in the cylinder, resulting in an abnormal increase in temperature and pressure in the combustion chamber. All of these factors increase the risk of engine knocking.
In summary, oil-burning engines are more prone to knocking due to local overheating, corrosion and abnormal cylinder pressure caused by carbon deposits, acids and metal particles produced by oil combustion. In order to reduce the risk of engine knocking, car owners should check and change the oil regularly to keep the inside of the engine clean and well maintained.