How did the smell of gasoline in the engine oil come from?

How did the smell of gasoline in the engine oil come from?

In fact, not only the engine oil of in-cylinder direct injection engine will smell of gasoline, but also the engine oil of EFI, direct injection and mixed injection will smell of gasoline. Let me briefly talk about how the smell of gasoline in engine oil comes from. Because gasoline enters the crankcase through the gap between the cylinder wall and the piston ring and pollutes the engine oil, the engine oil smells of gasoline! This statement is not completely wrong, but it is not rigorous! You should know that the combustion chamber of the engine is indeed positive pressure and the axle box is negative pressure. The gas in the combustion chamber may be pressed into the crankcase, but it is not the pollution caused by the gasoline vapor in the combustion chamber being pressed into the crankcase! In fact, part of the oil hangs on the cylinder wall and the piston evaporates to a diameter.

And why do these polluted oil vapors cause the oil in the whole crankcase to smell like gasoline?

The answer is that this part of the mixed steam of engine oil and gasoline must be separated by a "cyclone separator" after being pressed into the axle box (as shown below). After the mixed steam of engine oil and gasoline enters the cyclone separator, the low (light) density gasoline vapor is directly sent back to the intake manifold (or directly discharged into the cylinder) from the upper passage to participate in the secondary combustion, while the heavy (heavy) engine oil vapor gradually descends to the lower outlet for condensation and re-ignition. But this part of the engine oil was polluted by gasoline when it flowed back to the crankcase, so this part of the engine oil smelled of gasoline. But think about this separation work as long as the engine is started, it will continue to circulate, so that the engine oil in the crankcase will gradually smell like gasoline!

Turbocharged engines are basically popular in European and German cars, and the cylinder pressure before ignition is much higher than that of naturally aspirated engines! As mentioned above, the combustion chamber is positive pressure and the crankcase is negative pressure. When the turbine head is forced to intake air, the pressure in the combustion chamber is greater, which means that more mixed vapor of gasoline and engine oil is forced into the crankcase during the operation of the turbine head, that is, the "cross flow" is large! This crankcase PCV system has a special pressure limiting valve. In order to ensure that the crankcase is always in a negative pressure environment, once the "cross flow" is too large, the pressure limiting valve will open to release the pressure. Once this pressure limiting valve is opened, gasoline and engine oil vapor will not be separated by the cyclone separator, but will be directly discharged to the intake manifold (or the combustion chamber of the direct injection machine) for combustion, so that the engine oil that has not been separated will burn at the same time! There are many German turbocars, most of which squeeze the engine too hard and have a large gas flow. Piston rings and oil seals are also devastated, and the oil is often burned before it can be separated! This is why most turbine heads can't avoid oil consumption!