Oil change
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An oil change is the replacement of used lubricating oil with fresh oil in machine gears , engines or machines with circulating lubrication .
Change
The time or interval of the oil change and the type of oil to be used are determined by the manufacturers of the machine or vehicle. This point in time depends on the aging of the oil as well as the ambient conditions and the intensity of use of the machine. In the case of vehicles, these intervals are often determined on the basis of the mileage or combined according to mileage and time, in the case of other machines on the basis of the operating hours. Vehicles with a condition-based service display determine the point in time according to parameters that are recorded and evaluated by the sensors of the vehicle electronics and allow conclusions to be drawn about the actual stress on the oil.
Variable oil change intervals can be checked for due dates using a suitable oil quality probe, which usually also measures the oil level and temperature. In the case of large industrial units, the oil quality is also regularly checked by examining oil samples, thus determining the optimal time for a partial or complete replacement of the oil.
Stress on the lubricating oil in the combustion engine
Duties of the lubricating oil
In engines with pressure circulation lubrication, engine oil is sucked in from a reservoir ( oil pan , oil tank) by an oil pump and pumped through an oil filter to the various points in the engine that require lubrication. These are mainly the plain bearings of the crankshaft and camshaft, the connecting rod bearings, the bearings of turbochargers , the valve train and the cylinder liners of the engine cylinders. The pressure oil is also used as an operating medium for hydraulic actuators, e.g. B. for camshaft adjustments . In the case of block motors, there is also the lubrication of the gearbox and the clutch. In addition, the engine oil - especially in air-cooled engines - serves as a cooling medium that transports heat away from regions in the engine that are subject to high thermal loads, such as piston heads, cylinder heads or the bearing chambers of turbochargers. In order to achieve proper lubrication under all operating conditions, the engine oil - among other defined properties - must have a certain viscosity .
Wear and tear and consumption
Motor oil is exposed to a constant process of wear and aging. In addition to the inclusion of abrasion from the various storage locations which can be removed again through the oil filter only partially, the oil through is blow-by gases chemically claimed by transporting the unburned fuel or products of combustion from the combustion chamber past the piston rings into the crankcase in which the engine oil is located.
It is also necessary that a microscopically thin oil film remains on the honed liner wall with each piston stroke and is not stripped off in order to lubricate the piston in the cylinder and achieve a fine seal. In this way, this oil gets into the combustion chamber and is burned there. Other places where oil consumption occurs are the valve stem seals, which act as sliding seals to seal the intake tract at the upper end of the valve stem from the oil chamber in the cylinder head. Furthermore, oil goes through sweat and drip losses, z. B. on shaft seals or housing seals lost. This will gradually lower the oil level in the engine. For this reason it is advisable to check the oil level regularly. Excessive consumption can be caused by damage to the cylinder head gasket, valve gaskets or a piston ring , but rarely also by cracks around the cylinder head or engine block .
Oil multiplication and oil dilution
The lubricity of the oil and its chemical composition can also be adversely affected by the introduction of unburned fuel into the engine oil filling. The cause can be, among other things, regeneration cycles of diesel particulate filters , but condensates from unburned fuel are increasingly deposited in the engine oil even with continuous short-distance operation with a cold engine.
Oil level measurement
The oil dipstick (also called dipstick or oil stick) or a sight glass shows how much oil is still in the reservoir (e.g. oil pan). The oil level is specified by the manufacturer and should be between a defined minimum and maximum. For the measurement, the vehicle should stand on a level surface and be in the condition specified in the operating instructions - for example, the oil level must often be measured according to the instructions with the engine switched off and at operating temperature. Then pull out the dipstick, clean it and push it in again completely, as otherwise drops of oil from the cylinder head on the dipstick inside the engine could simulate an increased oil level. Now you can pull out the dipstick again and read the oil level.
Oil level above maximum means that the crankshaft constantly hits the oil and it foams up; the oil foam does not lubricate well and can cause damage. In addition, the foam slows the spraying distance of the oil, so that the piston running surface is not sufficiently lubricated. Overfilling has another disadvantage: if the oil level is too high, important ventilation holes in the crankcase can be covered by the oil level , which means that excess oil gets into the intake tract via the crankcase ventilation and is burned in the engine. This can result in significantly higher combustion temperatures, afterglow on the surface of the cylinder head and, in the case of gasoline engines, knocking due to premature ignition in the next cycle and thus damage to many components of the engine, including major engine damage and the catalytic converter .
If the oil level is too low, oil must be topped up to prevent the oil pump from sucking in air, which would cause an oil pressure drop. This is indicated by the oil pressure warning light . If this lights up, the engine is already being damaged. For this reason, oil level sensors are installed in some vehicles, which indicate that the oil level is too low before the oil pressure drops. The oil pressure light is switched by the ignition-switched plus from the oil pressure switch to the motor housing as a minus pole. The oil pressure switch is located in the oil channel behind the pump and after the oil filter . The oil pressure opens the contact. Oil pressure switches can be available with the same dimensions with different switching pressures. Multipole oil pressure switches have additional switches that are neutral in relation to the housing or sensor contacts for measuring oil pressure and oil temperature or are integrated in a bus system.
Oil change in an automobile
In the case of motor vehicles, an oil change usually means replacing the engine oil . Lubricating oil is also contained in the main gearbox and partly in the transfer cases, and hydraulic oil in automatic gearboxes , power steering systems or steering gears, depending on the design ; these mostly have a much longer service life, as they do not affect the combustion process. They do not have to withstand high temperatures and neither pick up fuel residues nor soot particles.
According to the manufacturer and workshop, an oil change should also be carried out every 12 to 18 months for vehicles that only travel 10,000 kilometers or less per year, because even with low mileage, the quality of the lubricating properties deteriorates due to aging, which leads to increased wear and tear There is a risk of piston seizure . Mineral oils are more susceptible to these aging processes than synthetic ones. According to other information, an oil change is only necessary after many years, if at all.
First, the old oil has to be drained and collected. The oil drain plug , which is located near the lowest point of the engine, is used for this. It is partially attached to the side and therefore protected. If you open this, the oil runs out of the engine and has to be collected in a tight container.
Motor oil must never get into the environment ( environmental pollution is a criminal offense). In Germany, used oil can be handed in when you buy new oil.
In most cases, the oil filter should also be replaced with the oil change . This filter catches dirt and metal particles, but can only do so until the capacity of the filter is exhausted. There are filters with the same dimensions and threads that have different flow resistances.
There are volume specifications with and without an oil filter for refilling with new oil. The oil level is checked using the engine's own oil dipstick .
Engine-specific oil specifications are always decisive as a minimum requirement. This is noted in manuals and operating instructions. If the engine is operated under changed circumstances such as a different climate (which has different viscosity requirements) or with LPG instead of gasoline (gas burns hotter than gasoline), the requirements for the oil may change. When operating with LPG, there is no contamination from fuel components and less soot. The same viscosity should be used when mixing (by topping up) oils. The designation of motor oil types (e.g. 5W-40) should always be interpreted in the same way: the lower the number in front of the letter W, the more fluid the oil is at low temperatures. The second number describes the viscosity at a temperature of 100 ° C. In addition to the conventional mineral oils, synthetic or low-viscosity oils can also be used. Although all 3 groups mentioned contain additives, the last two mentioned reduce the friction in the engine more intensively, which in turn can have a positive effect on fuel consumption.
Unalloyed engine oils must be used on veteran vehicles that do not have an oil filter . Unalloyed oils form oil sludge on the bottom of the oil pan , which to a certain extent binds undesirable foreign bodies and engine abrasion. When changing the oil, the oil pan must be dismantled and cleaned of oil sludge.
Web links
Individual evidence
- ↑ ADAC: Attention if the oil level rises - oil dilution in diesels with particle filters .
- ^ ZDF Frontal21 - Article on the subject of oil change ( memento from January 12, 2008 in the Internet Archive ) from January 8, 2008.
- ↑ http://www.api.org/~/media/files/certification/engine-oil-diesel/publications/mom_guide_english_2013.pdf (English).
- ↑ From the oil level to the oil change. November 3, 2017. Retrieved November 19, 2017 .