Engine oil contamination
Depending on the operating conditions, engine oils are exposed to varying effects. Therefore, it is very difficult to determine the effect of various conditions on the lubricant. Engines running for long periods of time at high speeds or under full load reach high temperatures. Under the influence of high temperature and atmospheric oxygen, the oil begins to oxidize. Oxidation products thicken the oil and can deposit on the top of the piston, in the piston ring grooves and on the valve stems. This can cause the formation of carbon deposits on the valve plates.
Oil thinning on gasoline engines
If the cylinders are too rich, the engine cannot develop maximum power or the engine is constantly running too cold (urban cycle), soot is inevitably formed. Soot, burnt oil and other products, unburned fuel itself and liquid condensation lead to the formation of sludge, acid and asphalt. Unburned fuel settles on the mirror of the cylinders and flows into the crankcase, while the oil film on the cylinders and pistons is washed off. Consequences: insufficient lubrication of the sliding surface of the pistons and oil dilution, which reduces the lubricating properties of the oil, depending on the amount of fuel that has penetrated. If the dilution is too high, it may be necessary to change the oil prematurely. Since gasoline particles evaporate from the oil in a hot engine, the oil level should be checked, especially in winter (many cold starts - high fuel content in oil).
Engine oil viscosity
Viscosity is the resistance of a liquid to the internal movement of its layers. Depending on the temperature, each oil tends to change its viscosity. As the temperature rises, the oil becomes thinner. Because of this, the adhesion and strength of the oil film deteriorates. When cold, the oil becomes viscous, and the internal friction resistance increases.
Application area/Viscosity classes
On a cold engine, the oil must be thin enough not to interfere with the operation of the starter and to flow to all lubrication points as quickly as possible when starting. This requires the use of an engine oil with a viscosity that changes the least at different temperatures. The viscosity of an oil has the same meaning as the internal friction of an oil and is designated by the SAE system (Society of Automotive Engineers), eg SAE 30, SAE 10, etc. High SAE numbers for thick oils, low SAE numbers for thin oils. Viscosity does not give an idea of the lubricating properties of the oil.
All-weather oil
For MAZDA 323 engines, multigrade oil should be used. All-weather oils have the advantage that they can be used in both winter and summer. All-weather oils are based on liquid seasonal oils (e.g. 15W). By means of so-called thickeners, the oil is stabilized in the hot state, so that the necessary lubricating properties are ensured for each state. "W" in the SAE system indicates that the oil can be used in winter.
Oils with antifriction additives (light running oils)
Light running oils are multigrade oils with anti-friction additives, so fuel savings of up to 2% are possible. Lightweight oils have a low viscosity (for example, 10 W - 30. They use an unusual base (synthetic oils). When buying a light-running oil, you should pay attention to the fact that this oil is suitable for MAZDA. Because adjacent SAE classes overlap, short-term temperature fluctuations are acceptable. It is allowed to mix oils of different viscosity classes with each other if it is necessary to add oil and external temperatures do not correspond to the viscosity class of the oil in the engine. No additives should be added to the fuel or oil.
Engine oil specification
For modern engines, only HD oils are allowed. HD oils are oils whose lubricating properties have been greatly improved by the addition of various substances. These additives provide stronger protection against corrosion, oxidation, especially a reduced tendency to form sludge in the crankcase, better viscosity, cleaning and dissolving properties. Cleaning and dissolving additives not only reduce the formation of sludge in the engine, but also have the ability to dissolve deposits and separate them and other contaminants into small particles and hold them in suspension in the oil pan so that when the oil is changed, the contaminants drain with it. HD oil quality is designated by API classification (American Petroleum Institute). European manufacturers are also guided by this system.
The designation consists of two letters.
The first letter indicates the scope:
- S = Service is for gasoline engines;
- C = Commercial for diesel engines.
The second letter denotes the quality in alphabetical order.
API SG oils for gasoline engines and CE oils for diesel engines have the highest quality.
Engine oils specified by the manufacturer for diesel engines are not suitable for gasoline engines. There are oils suitable for both diesel and gasoline engines. In this case, both designations are on the bank (e.g. SF/CD). for MAZDA 323 with gasoline engines engine oils SE, SF and SG are defined according to the API specification, for diesel engines API - CC and CD.
Oil consumption
Speaking of oil consumption in an internal combustion engine, we mean the amount of oil that is consumed due to the combustion process. Under no circumstances should oil consumption be confused with oil loss resulting from leaks in the sump, cylinder head cover, etc. Normal oil consumption occurs due to the combustion of a small amount in the cylinders, due to the removal of combustion residues and particles wear products. The oil wears out due to the high temperatures and high pressures that occur in the engine. Oil consumption is also greatly influenced by external factors, driving style, as well as the accuracy of parts manufacturing. Oil consumption can be a maximum of 1.0 liters per 1000 km.
When the limit mark is reached, the oil must be topped up.
Attention! Do not pour large amounts of oil at once. If too much oil has been poured into a car with a catalyst, the excess must be drained, otherwise unburned oil will enter the exhaust system and can destroy the catalyst.