Effect of Base Oil and Additives on Combustion Chamber and Intake Valve Deposits Formation in IC Engine

There is significant contribution of engine oil in deposit formation on different parts of engine viz. combustion chamber, Intake valve and piston & ring assembly. Basic parameters involved in deposit formation are surface temperature, operating condition of engine, condensation & polymerization of engine oil components. Deposit forming rate is inversely proportional to the surface temperature. Critical surface temperature of combustion chamber is about 370°Cfor oil derived deposits; it is 60°C higher than the fuel derived deposit. Higher oil consumption rate and higher base oil boiling ranges tend to increase the deposit level in combustion chamber whereas high boiling base oil can keep a valve clean. Tests have shown that IVD increases when volatility of base oil becomes higher due to condensation and polymerization of engine oil additives. Furthermore VI improver, metallic detergent, ashless dispersants have considerable effect on IVD formation. However oil formulation is the dominating factor that determines whether oil will keep a valve clean or form heavy deposit.