Engine oil selection

Absolutely all drivers periodically face the need to change the oil in the engine of their car. And at this moment, the agony of choice begins – how not to miscalculate and decide on the best option specifically for you and your car. What should be paid more attention – let’s figure it out.

Why does a car engine need oil?

There are different approaches to the classification of motor oils, and for a better choice, you need to familiarize yourself with some of them.

Firstly, according to the method of obtaining the finished product, I divide all automotive oils into three large groups: mineral, synthetic and semi-synthetic. Mineral oil is made by distillation from waste oil. It is environmentally friendly, well lubricates all the necessary engine parts, and is relatively inexpensive. Semi-synthetic oil is essentially a transitional option (or a hybrid – whatever you like) from mineral to synthetic. It contains from 30 to 50% mineral components and 50 – 70% – synthetic. According to the characteristics, it is slightly better than the “pure” mineral, but not the limit of perfection. Synthetic oil is also made from petroleum products, but more carefully processing the original product. It has the best characteristics (high viscosity, long service life, less harmful impurities, etc.).

Secondly, depending on the main characteristics of the oil, its viscosity, oils are divided into winter, summer and all-weather.

Winter engine oil is indicated by the letter “W” and the number in front of it: SAE 0W, 5W, 10W, 15W, 20W, 25W.

Summer engine oil is designated simply by a number: SAE 20, 30, 40, 50, 60.

Multigrade engine oil, the most common, is a combination of winter and summer designations, for example, SAE 5W40, SAE 10W-40.

Thirdly, depending on the engine where the oil will be poured, engine oils are distinguished for gasoline and diesel engines.

Before you start choosing engine oil for cars that are in long-term operation, you should determine whether your car has any problems. For example, is there any waste, if “yes”, then what kind (how often do you have to add oil?). What happens to oil pressure? Are there any unusual sounds that are not characteristic of normal engine operation? And so on. If there are no external deteriorations in the operation of the engine, then when choosing engine oil, we first of all pay attention to:

Engine oil selection

1. The right choice of performance properties of the oil. We choose oils with classifications and tolerances recommended for this car model. At the same time, you should not choose oils with the minimum allowable requirements (what they are according to SAE, API). It is better to dwell on oils of the latest classifications, in the worst case (with limited financial resources) – on “middle oils” (what they are according to SAE, API). Although they are inferior in quality to the latest engine oils, their properties are still higher than those of oils with minimum acceptable performance requirements (which they are according to SAE, API). And it is categorically impossible to choose oils with obviously inappropriate, understated indicators and tolerances. This statement is also confirmed in the new catalogs for the use of motor oils. Pay attention to the fact that in the latest catalogs there are still models of cars from very old years of production, but you will no longer find engine oils with old classifications, for example, with the API SF / CC classification. Therefore, for “veteran cars”, it is better to use oils of more recent developments and classifications.

But there are no rules without exceptions. There are restrictions on the use of some modern oils in cars of earlier models. First of all, this applies to oils with reduced high temperature shear viscosity (HTHS – High Temperature High Shear). In new models of some vehicles, low viscosity oils (HTHS<3.5 mPa•s) are recommended to reduce fuel consumption, and the engine design is specifically designed for the use of these special low viscosity oils. But the use of such energy-saving oil in cars of earlier years of production can lead to disruption of the normal operation of the engine up to its failure. This rule applies to oils with the following classifications and approvals: ACEA A1 / B1, A5 / B5, ACEA C1, C2; VW 503.00/506.00/506.01; BMW LL-01FE (Longlife Oil-01FE); Ford 913 A/B or special instructions for reduced dynamic viscosity HTHS. Oils with these specifications are not suitable for old cars.

2. Choosing the Right Engine Oil Viscosity. As mentioned above, the viscosity of the oil is determined by the operating conditions of the car and its condition. It is the second criterion that becomes decisive when choosing an oil viscosity for used cars. You should also remember and take into account problems during engine operation – waste, oil pressure, etc. If such violations are not observed, there are no restrictions on the choice of oil viscosity. In this case, you can only be guided by the climatic conditions of the car and your own wallet. To date, the optimum viscosity in terms of all-weather use, energy saving, low-temperature and high-temperature parameters is an oil with a viscosity of SAE 5W-30. For Japanese and American cars, regardless of the year of manufacture and age, this viscosity is still optimal. A cheaper alternative for such vehicles may be 10W-30 viscosity oil. But for European hard-working cars, it is better to use oils with a viscosity of SAE 5W-40 or 10W-40.

3. If there are any deviations from the normal operation of the engine, special attention should be paid to the choice of viscosity. First of all, low-viscosity and energy-saving oils should be abandoned. Their reduced low-temperature, and in some cases, high-temperature viscosity can only exacerbate existing problems, because under conditions of engine wear and violation of its operating modes, the resulting protective oil film becomes thinner, less durable and no longer provides reliable protection of surfaces from wear and damage. In addition, low-viscosity oils have a higher volatility. This increases the loss of oil for waste and contributes to its even greater consumption. That is, in such problematic cases, oils with a higher viscosity at operating temperatures are required. And oils with viscosities 5W-50, 10W-50, 10W-60 come to the fore, 15W-50, 20W-50. But at the same time, when determining the viscosity, one should not forget about the performance properties of the oil. Only a competent combination of viscosity and oil specifications will extend the life of even a worn engine and delay its overhaul.

Engine oil 5w30 or 5w40. What to choose?

4. Choosing the right oil base. This oil selection criterion applies more to engines with problems. It is no secret that mineral, semi-synthetic and synthetic oils can have identical performance properties, i.e. have the same classifications and specifications and differ only in viscosity and type of base. The difference in the viscosity of oils of different nature (with the same type of performance properties), in some cases, makes it possible to smooth out the existing problems of old engines.

For example, SAE 15W-40 mineral oils have a slightly higher kinematic viscosity at 100 degrees Celsius than most 5W-40 synthetics. This allows worn engines to form a stronger and thicker lubricating film at operating temperatures. This provides better wear protection and more stable oil pressure in the system. Reduced consumption and loss of oil for waste. It gives the impression of a better performance of a worn engine on mineral oil in comparison with semi-synthetics and synthetics.

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