Why Does a Car Consume Oil?
Consumption of one liter of oil per 1,000 kilometers can be understood as normal, however, there is nothing established, since consumption depends on the type of engine, the type of oil used and the driving style. For example, if we do a conservative driving, we will hardly notice variations in the oil level when measuring it with the dipstick. It is easy to detect when a car consumes oil because the smoke that comes out of the exhaust will be bluish.
Beyond the fact that there are leaks, external (easily identifiable), and internal, the latter is more difficult to identify and solve ... where does this oil waste come from? Well, in general, three points, which we can quickly identify:
Oil Consumption Due to Piston Lubrication:
The oil lubricates the space between the pistons and the cylinder walls. Part of this oil enters the combustion chamber, where it burns. When the engine rotates at high speeds, the number of lubricating oil increases so that the amount of oil consumed increases. This process is divided into three phases:
- Inlet, the piston leaves a layer of oil that permeates the cylinder.
- Compression, the oil is led into the combustion chamber through the fire segments.
- Descent, the walls are impregnated with oil that is burned along with fuel by the exhaust.
If an engine does not burn oil it means that there is no necessary oil layer between the piston and the cylinder, which would indicate that there is no lubrication. Depending on the gaps between the parts, more or less lubricant will enter the combustion chamber. New engines consume less oil as there is less clearance between parts.
An engine ends its useful life when there is the excess clearance between cylinders and segments because too much oil rises into the combustion chamber and burns out of the exhaust. Symptoms to identify this problem are blue smoke coming out of the exhaust and engine performance, which is decreasing due to loss of compression.
Oil Consumption Due to Valve Lubrication:
A valve is a kind of long nail with a large head. Through them, the mixture of air and fuel enters, and the residual gases of the combustion that causes the movement to leave. The oil lubricates the space between the valves and the valve guides. As with piston lubrication, some of this oil enters the combustion chamber, where it is burned. The intake valve is the one that allows the mixture to enter for combustion. The valve stems prevent oil from getting there, but there is always a minimal layer of oil that burns in the combustion chamber.
Oil consumption can also be caused by valve seals, which do not allow the oil to flow down into the combustion chamber. When the piston begins to drop, it absorbs the mixture that passes through the gap left by the valve when opened. So there is higher oil consumption when the vacuum is higher in this hole, such as when the engine idles or decelerates. Oil is also consumed through the exhaust valve; in this case, it evaporates due to the high temperatures caused by the gases themselves
Oil Consumption by Gases Escaping from the Cylinder:
The oil mixes with the gases that escape from the cylinder, which are captured by the positive crankcase ventilation system and are sent to the combustion chamber, where they are burned. The quantity of gases in the cylinder increases when the engine runs at high speeds, and the greater the quantity of gases, the greater the consumption of oil.
