Useful
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1. What is the difference between more expensive and cheaper lubricants?
High quality lubricants exceed standard requirements. They are more reliable, provide more protection guarantees, and they therefore cost more. Some lubricants only marginally comply with test requirements, while others significantly exceed them. Besides, each testing costs. It is worth mentioning several other price influencing factors – the high production level of the base oil and its chemical additives, plus the quality control system used in its production. Therefore, in paying for a high class oil you acquire a reliable guarantee for car engine protection and the reliability of other mechanism’s operation.
2. What is the difference between synthetic and mineral greases?
Synthetic greases are produced during complicated chemical and physical processes by separating, modifying, and combining (and in this way changing) the molecules found in ''green'' petroleum. On the other hand, mineral greases are only extracted by separating and purifying the molecules already existing in ''green'' petroleum during the distillation process.
3. What are the advantages of using a more expensive completely synthetic oil, even though synthetic technologies or mineral oil are recommended for the car?
The properties of synthetic lubricants significantly exceed the minimum required specifications of engine manufacturers. The state of the art formulas of chemical additives which are used in synthetic lubricants ensure better characteristics of engine cleanliness, protection against wear, and oxide separation during the whole interval of oil service. Synthetic lubricants are more fluid at cold temperatures because of a higher base oil viscosity, so fuel is saved, and the car’s battery and starter are spared. Synthetic lubricants are much more resistant to loads and oxidation caused by higher temperatures. For these reasons, many manufacturers allow applying longer replacement intervals of these lubricants.
4. Why does the oil in the engine get black within a certain period of time? Does that mean its quality is poor?
Engine lubricants are specially created in order to stop deterioration and keep the engine clean. With the help of detergents, the oil cleans deposit components from the engine and burns caused by high temperatures. Dispersants located in the oil maintain these particles in suspension, not allowing them to clump into bigger particles and deposit or burn again. So the black colour of oil during operation is usually a feature of quality. It means that by changing the oil after the defined interval, you are also removing impurities from the engine.
5. Oil consumption: is the reduction of oil quantity during engine operation a problem?
Any engine consumes a certain quantity of oil during operation. When the piston of the engine moves down, a small part of the oil remains unmoved by the piston rings and it burns in the cylinder during fuel mixture ignition. Oil also evaporates in the casing and these vapours get out from the engine to the atmosphere. In engines of older construction even the consumption of 0.35l per 1000 miles is supposed to be normal. In state of the art design engines, which need the newest low volatility degree synthetic oil, the consumption of oil may be almost unnoticeable. Besides, oil consumption depends on the season. It is consumed less in winter because the engine has no time to heat up to the proper operating temperature. Besides that, in winter when a car only makes short distance trips, much more unburned fuel may get into the oil in the crankcase (even up to 10% of the oil quantity). That is why the quantity of oil can even visually increase. Since high quality oil accumulates combustion products and small particulates, it oxidizes. Its consumption and filling during the service period makes the oil fresher. So, if the consumption of oil does not exceed moderate limits and is not a technical problem of the engine (leakage through seals and cracks), you should not worry about it.
6. Can lubricants of different manufacturers be mixed? Will synthetic lubricants mixed with mineral ones react chemically?
All lubricants produced by large companies are inspected during special tests, e.g. API, ACEA and etc. One of them is the test of oil miscibility. Lubricants complying with highest level (e.g. API SL/CF) or lower level (e.g. API SJ/CF) standards can be mixed. It often happens that it is not known what oil is in the engine or there are suspicions that chemically aggressive additives have been used which provide a temporary effect when reselling the car (e.g. for compression elevation and similar). In those cases it is recommended to completely change the oil.
7. Oil consumption has significantly increased after having started to use the oil of a new manufacturer or after having replaced mineral oil with synthetic. Does it mean that the newly filled oil is not of sufficient quality?
Usually the engine needs some time to get used to a new kind of oil. Since lubricants of different brands have a different formula of chemical additives, the operation of the new oil may differ from the previous one. Increased oil consumption and leakage through seals are most the common problems experienced in altering the type of oil used. Of course, that is also influenced by the wearing of the piston group of the engine. More oil gets in to the engine injection cell and is simply burnt and emitted together with oxides. After some time, when the engine gets used to the new oil these problems usually disappear. So an ambivalent statement that this new oil is not of the same quality as the previous is not grounded. Besides, having replaced mineral types with synthetic, the lower viscosity of the latter and better washing additives also make the same effect.
8. Influence of the driving regime on the interval of oil replacement: In what cases can the oil replacement interval be extended?
It may seem that there are many advantages of oil replacement interval extensions: oil, filter, replacement service, purchase costs, and etc. are reduced. However, a longer oil replacement interval will ''load'' the oil used especially in modern engines where the oil consumption (and additional filling during the interval) is low. Modern engine lubricants exceed the newest international specifications and are tested according to standards defined by all the main engine producers, such as BMW, Daimler Chrysler, General Motors, Peugeot-Citroen, VW, and etc. Whenever allowed by the manufacturer, lubricants may be changed after a longer interval, however only according to the recommendations of the engine manufacturer. Engine manufacturers ground the recommended oil replacement intervals on statistical data of the average user. Both the required oil quality level and oil replacement interval and shortened oil replacement interval under heavy operation conditions are indicated in the technical instructions of the car. There is only one conclusion – it is necessary to follow the information indicated in the technical manual of the engine manufacturer and take into consideration the driving conditions.
9. What is viscosity?
Fluid that is extremely resistant to flow can be called viscous. For example, water has low viscosity in comparison with honey, so in this case we say that honey is more viscous than water at the same temperature of these materials. Viscosity of good quality oil changes little upon changes in temperature and the influence of other consumption conditions for a long time.
10. What should the temperature of an engine be during an oil change?
At operational temperature (~100°C), oil is more fluid than when the engine is cold. At room temperature, oil is thicker and sticks better to the vertical surfaces of the engine. It is also suspended in flat, horizontal spaces of the engine. When changing the oil at room temperature, you will only remove 60% to 70% of the old oil. However, having heated the engine to operational temperature, you will be able to remove from 90% to 95% of the old oil and this is fully enough.
11. Is it possible or necessary to use additives which, according to the manufacturers, improve the operation of the engine?
This is not desired and not necessary because it is very difficult to foresee the outcome. All the lubricants of famous manufacturers have a package of effective additives. During the design and production of oil, not only are special quantities of additives selected, but the balance of their effect on each other is also coordinated. The biggest danger is that this balance may be destroyed after having added even the best additive. This effect will be ''zero'' in the best case. It will be negative in the worst case.