What Causes Blue Smoke from a Car?

[DiChase]

Blue smoke from a car is caused by factors such as incorrect engine oil viscosity selection, carbon buildup on piston rings, and aging valve stem seals. The specific reasons are as follows: Incorrect engine oil selection: Manifested by no blue smoke during cold starts in the morning, but slight blue smoke emission after the engine warms up. Previously no blue smoke appeared, but it occurs after switching to another type of engine oil. The car maintains acceleration capability, but exhibits excessive oil consumption and increased engine noise. Carbon buildup on piston rings: Carbon deposits cause piston rings to lose tension, resulting in poor sealing that allows oil to enter the combustion chamber through gaps. This leads to reduced power output, decreased cylinder compression sealing performance, and relatively increased oil consumption. Aging valve stem seals: Hardened valve stem seals fail to expand and contract with temperature changes during engine operation. This allows oil to enter the combustion chamber during cold starts. A stuck PCV valve permits combustible mixture to enter the crankcase, thinning and contaminating the engine oil, which then enters the combustion chamber and accelerates oil consumption.