What happens when car valve seals are not tight?

[Karl]

When car valve seals are not tight, the following issues may occur: Oil leaking into the combustion chamber due to poor valve sealing typically results in blue smoke from the exhaust; Prolonged operation with this condition can lead to carbon buildup on the valves, causing improper valve closure and incomplete combustion; It can also cause carbon deposits in the combustion chamber and fuel injectors, or clog the catalytic converter; Additionally, it may result in decreased engine power, significantly increased fuel consumption, damage to related components, and notably reduced spark plug performance. The main reasons for poor valve sealing are the mutual impact between the valve and valve seat, which causes grooves and widening of the working surfaces, especially when the exhaust valve is frequently exposed to high-temperature gas erosion, leading to oxidation, burning, and the formation of spots and grooves on the working surfaces.