What is the difference between synthetic and mineral water. To work in unstable environments

05.04.2019

When the range of oils became more diverse, there were disputes about which fluid to choose. Each type technical fluid there are their own supporters, but in most cases each of their arguments is based on myths and assumptions, so the process of choosing an oil product for the engine of your car should be thoughtful and thorough. Whether to choose mineral or synthetic oil? Or maybe it's worth buying semi-synthetics? And how to figure out which oils are mineral and which are synthetic?

How to distinguish mineral oil from synthetic? These oil products have differences at the molecular level. Synthetics have a structure that has been achieved through lengthy experiments and tests aimed at acquiring liquid necessary qualities. However, this species oils have a molecular structure that is inherent in them by nature. If in some properties synthetics begin to yield to mineral lubricating fluid, then immediately begin to work to correct the situation.

Again, the fact is that the “mineral water” cleans the components of the power unit regularly and quite effectively, and synthetics, due to viscosity, can clean the entire engine quickly. And it is for this reason that filters and oil pipes begin to clog with deposits of fragments from the engine. If in such a situation the control and inspection of parts lubrication system carried out rarely or incorrectly, this may result in the effect of " oil starvation", which will damage the engine.

Based on this information, we can conclude ο how mineral oil differs from synthetic:

differences at the molecular level;
the difference is in how the coolant (lubricating fluid) reacts to temperature environment;
fluidity of liquids: mineral oil at low temperatures becomes viscous, while synthetics have increased versatility;
stability indicator: the engine can fail if mineral-type oil additives burn out.

Watch a video about which is better to choose synthetic or mineral oil?

Features of mineral oil

In the production process of this oil product, agricultural crops or a purified product obtained during the processing of fuel oil are used. Due to the simplicity of this technology, SF is cheap and affordable. One of the advantages of "mineral water" is an increased degree of efficiency in operation, minimal mechanical influence at the time of interaction with the nodes of the power unit, which are moving. In addition, mineral and synthetic oils can be mixed.

However, it should be borne in mind that all the advantages of this lubricating fluid will manifest themselves if an acceptable temperature range of 10-25 degrees Celsius is provided. In other situations, you will need to use additives. It is here that the most obvious minus of using mineral water is hidden: additives can burn out when elevated temperature, and at low application lubricant composition becomes more difficult due to the increase in the viscosity coefficient.

Along with the two types of motor fluids described, there is an intermediate option - semi-synthetics.

Semi-synthetic is a blend of synthetic and mineral oils. Experienced experts advise diluting one liquid into another in equal proportions, or taking mineral and synthetic oil products in a ratio of 70/30, respectively.

This coolant is obtained by molecular synthesis. Thus, when using synthetic oils, it is possible to achieve high rate quality, stability, independent of temperature regime and other environmental factors.

It is advisable to opt for this liquid based on environmental conditions: area of residence, climatic features, the specifics of driving a vehicle, etc. Of course, it should be understood that this type of LF cannot be found in natural conditions, but in everyday life it has already become extremely familiar, so drivers do not even make assumptions about its origin.

Compared to other types of coolants, this one is the most expensive. But if we take into account some of the nuances of the climate, such as: low temperatures, then such a SJ, perhaps, will become a necessity, and not a spontaneous desire.

If you rely on the provided differences between the two types of motor oils in the question of which is better - mineral or synthetic oil - then the answer may seem obvious: of course, synthetics are a priority, so you should choose it. But in reality, not everything is so straightforward and unambiguous. There are situations in which it would be more correct to dwell on a mineral oil product, since it is more a budget option, beneficial when there is no need to overpay.

In addition, there are a number of circumstances when the use of synthetics is even prohibited. First of all, this is true for Vehicle having high mileage. Their seals have already worn out enough, which leads to leakage. Therefore, if we take into account high value the fluidity of synthetics, it can be understood that it will often “leave” the power unit. Therefore, you will have to deal with overspending of fluid and its constant addition. If your vehicle belongs to domestic auto industry, and the number of "passed" kilometers is quite large, take the "mineral water" without hesitation.

Again, these oil products have an undoubted advantage - due to them, many deposits on the mechanisms, components and components of the car are washed off over time. The situation is different with synthetics - deposits are scraped off in large pieces, which in the future can clog filters and the oil flow system.

Now, knowing which oil is better - mineral or synthetic, a motorist will be able to make right choice and extend the life of your vehicle.

Watch the video on whether motor oils can be mixed. Also tell in

If you love your car and want it to give you joy and drive you as long as possible without any problems, then you need to monitor and make a replacement in time. This is because the gearbox is a part that is constantly working under load. Sharp starts, untimely gear shifting, the weight with which the car is loaded - all this and much more creates a load. In the box, gears, shafts and many other components are constantly rubbing, and so that all this does not wear out once again, it is necessary to carry out "revisions" from time to time. It does not matter what type of gearbox you have installed: mechanics or automatic, in any case, pay due attention to your car.

Mixing mineral and synthetic oils is strictly prohibited.

Lines of operation of the transmission before changing the oil in it

Due to the fact that during the friction of the internal parts of the gearbox during the use of the car, small metal particles are deposited in the oil, in the future there may be serious problems which will lead to the repair or complete replacement of the transmission. For a manual transmission, the recommended mileage is 100,000 kilometers, or replacement should be done every seven years if the car is used by the owner on very rare occasions. But if you suddenly began to notice extra noise from the box, you need to urgently check the lubrication level. In cars with automatic transmission replacement should be done sooner. Approximately once every 90,000 kilometers or every six years.

We begin to select the right transmission lubricant

If it's time to change the lubricant in the box, the first thing you should pay attention to is manufacturers or specific models lubricating fluid provided car manufacturer in the owner's manual for the specific vehicle. For mechanical transmissions it is necessary to choose ordinary gear oil, in contrast to the machine for which it is used special liquid, which is abbreviated as "ATF". In no case should this be forgotten, because this liquid is specifically for high-quality lubrication of internal components.

Also, from time to time, you need to look at the parking space where the car has been standing for a long time to check for oil leaks from the transmission. If you find a puddle of gear lubricant under your car, you should immediately do a full inspection of the gearbox. Experts recommend changing the transmission lubricant before the onset of frost. Everything is related to the fact that sharp drop temperatures, these products tend to lose their properties.

Mineral or synthetic oil?

When choosing an oil, there are two main points to consider. Now we will consider them. Synthetic gear lubricant is good in that it is less viscous than mineral and its thickness does not depend on temperature, which means that the range of temperatures at which it is used is much greater than when using mineral water. Also, synthetics are less prone to aging, which prolongs the period of its use.

When choosing a gear lubricant, one must take into account the degree of wear of various rubber parts, since over time they lose their elasticity. If you have doubts about the condition of the rubber elements of the transmission, then you should not fill in synthetics. The fact is that it is liquid, and parts that have lost their acceptable elasticity will not be able to keep the lubricant inside the transmission, which will cause a leak. This happens due to the use of mineral water or semi-synthetics before synthetics.

These two types of oil, after entering the box, form a coating on the rubber components. And when synthetics are poured after replacement, it washes away plaque. If you are using the vehicle at very low temperature indicators, then winter groups of oils should be used. They do not freeze in the box, which prevents wear of its parts. Index W indicates such a group of lubricants. If, however, at temperatures below -30 degrees you use the usual lubricant, you can wait for the start of problems with the operation of your transmission.

Universal gear lubricant to use is 80w90 (can be used at temperatures above -30 degrees). For use in cold climates, 75w80 is suitable, it retains its usual viscosity down to -40 degrees.

What happens if you mix different types of gear lubricants?

Now the answer is for those who are thinking about mineral water with synthetics or semi-synthetics. So, in no case should you mix, all three types of lubricants have a different base, and when mixed, we get a precipitate of solid particles, which will destroy our gearbox from the inside, instead of preventing unnecessary wear.

conclusions

Now to summarize, the following points must be taken into account:

First, the condition of the rubber products inside the gearbox to prevent leakage.
Secondly, we make a report for ourselves, under what weather conditions we will use the car so that there are no unexpected "surprises" in winter time of the year.

Now you know the main properties of different types gear oils, which will help you make the right choice, thereby you can extend the life of the components of your box.

Mineral engine oil made from natural raw materials - oil. In rare cases, a similar product is obtained by processing crops. The mineral base is a natural product; it differs from semi-synthetic and synthetic motor oils at a significantly lower price. It is used to lubricate motors with high mileage and a significant degree of wear.

By distillation of crude oil and further purification, a natural mineral product is obtained. Relatively simple technological process obtaining such oil explains its low cost. However, the following features should be taken into account: mineral water has a high volatility and does not differ in stable performance.

In its pure form, the product obtained by distillation of oil (fuel oil) is not used. In order for it to be able to protect the parts of the power unit, special stabilizing additives are added to it, so the desired effect can be achieved.

Mineral oils are liquid mixtures of high-molecular hydrocarbons, products of oil refining (fuel oil distillation) with subsequent multi-stage purification. The boiling point of such hydrocarbons is between 300 and 600℃, and the chain structure is unstable. Different in length and configuration, they lose their original properties under thermal influence.

Purification of the resulting mixtures is to reduce the sulfur content by hydrotreating, removing paraffinic hydrocarbons and tars. At present, the process of purification by hydrocracking has become widespread, this has allowed the mineral base to technical properties close to synthetic oils.

About 12% of stabilizing components are added to mineral oils used as the basis of motor fluids for cars. These substances make it possible to provide the product with anti-corrosion, detergent properties and optimum wear resistance.

Mineral oil production process

The production technology consists in the distillation of petroleum products. Hydrocarbons in the composition of natural oil are unstable, they have a heterogeneous molecular structure. It is this quality that makes the resulting mixture unstable at different temperatures.

For getting motor mixtures natural ingredients are used as additives. But before the oil enters the engine lubrication system, the oil product obtained by distillation undergoes several degrees of purification. To improve the structure of unstable hydrocarbon compounds, several procedures are carried out:

removal of harmful substances such as resins, acids and sulfur compounds;
hydrocracking. This method allows not only to effective cleaning obtained raw materials, but also change the length of hydrocarbon chains. Thus, stability is achieved, and the lubricants produced by the hydrocracking method are not inferior in their operational properties synthetics.

The base oil base used for the production of motor fluids may have different viscosity characteristics.

Specifications

The main indicator of motor oils based on both mineral and synthetic base, is the viscosity. In mineral water, this indicator changes under the influence of temperatures: the lower the thermometer reading, the higher the viscosity.

Viscosity index - an indicator of the dependence of viscosity properties on temperature, indicates the level of thinning. The higher this index, the better quality oil. For example, at lubricant, which does not include stabilizers, the index readings range from 85 to 100, and for a lubricant with stabilizing additives, it reaches 120.

A low value indicates the difficulty of a cold start in winter period, and exposure to friction at high temperatures ah summer. When choosing a mineral motor oil, it must be taken into account that the viscosity decreases with increasing temperature, and increases with negative thermometer readings.

The thickness of the oil film formed by the lubricant directly depends on the viscosity index. For the stability of the film layer, in addition to the main additives, extreme pressure additives are used.

In addition to the main qualities, it should be noted a few more, no less important:

flash point. This factor is important for the reason that high molecular weight carbohydrates are used in production. Fast flash rate will increase lubricant consumption;
freezing temperature. The limit of the minus value at which thickening, crystallization and loss of basic properties occur;
alkaline number indicates the degree of neutralization of acids, providing anti-corrosion protection;
acid number indicates the presence of products formed during oxidative reactions.

Advantages and disadvantages

By their own technical specifications standard mineral oil loses to lubricants on synthetic and semi-synthetic bases. Mineral lubricants are able to "bring to life" worn rubber seals. This is especially true for vehicles with a mileage of more than 500 thousand km.

But the main advantage is still the low cost of mineral water in comparison with synthetic products. Motorists should also take into account the fact that the replacement of mineral motor oils has to be carried out more often.

If you turn to positive aspects of the product in question, we can distinguish the following:

mineral oils gradually wash away carbon deposits from parts, do not cause clogging of the lubrication system and motor channels;
less aggressive to rubber parts, unlike synthetics and semi-synthetics;
optimal filling of gaps in internal combustion engines with a high degree of wear, therefore, in cars with significant mileage, the use of mineral oil is most justified. At constant use mineral water during long period switching to other basic bases is undesirable, since synthetics will not cope with a large amount of soot.

Traditional mineral oil has been used as mechanical lubrication. Alternative option hydrocracking engine oils are produced by distillation and deep purification with a change in the structure of hydrocarbon chains. According to its technical characteristics, it is most similar to synthetics.

But here one must take into account such an important minus: such lubricants quickly age, and they have to be changed 2 times more often. The aging of the lubricant is due to the fact that the additives burn out quickly.

The disadvantages of mineral water in the first place include instability. So at sub-zero temperatures the lubricant thickens and crystallizes, it is poorly pumped at the time of start-up. The starter can hardly cope with the crankshaft, which is in a dense mass. In addition, the thickened lubricant is not able to reach the surfaces of the parts in the right amount and protect them from wear.

What engine fluid to use in a particular case will be prompted by the technical documentation motor vehicle. Mineral oils are used in old-style power units with high mileage. It is better to use them in the warm season, in other words, to avoid a large temperature difference during operation.

Mineral engine oil on modern market is not very popular, many motorists prefer synthetics or semi-synthetics. However, most buyers are unaware that some famous brands sold under the brand of synthetics, a processed mineral mixture.

Mineral motor oils are a product of the processing of petroleum hydrocarbons. Their structure consists of molecules that are inhomogeneous in shape and structure - this leads to instability of the characteristics motor fluid under various temperature conditions.

Mineral water, unlike synthetic and semi-synthetic lubricants, is of natural origin; natural additives are used for its manufacture. Engine oil manufacturers improve the structure of mineral mixtures in two ways:

Removal of impurities from the liquid of harmful resins, acids, sulfur compounds. This method makes it possible to obtain an oil base without harmful substances, but the viscosity of the mixture at high and low temperatures will change.
More effective method Processing of mineral liquids is considered hydrocracking technology. Thanks to it, not only are removed from the base harmful substances, but the length of hydrocarbon chains also changes. Thus, the hydrocracking technology makes it possible to obtain products with stable viscosity characteristics to temperature differences. Hydrocracked oil will retain its properties better throughout the entire operating period (than pure mineral oil), it will practically not differ from synthetic mixtures.

Synthetic lubricants are obtained using the synthesis of hydrocarbon compounds, their cost is much more expensive than hydrocracked products. If you are looking to purchase a fully synthetic automotive oil not a processed product mineral base, synthetics differ in the designation in the classifications, and also note: the inscription on the canister "Full-synthetic" is fully synthetic.

Advantages and disadvantages

The main and most important difference between a mineral motor oil and a synthetic or semi-synthetic one is the resistance of the mixture to various temperature conditions of the power unit. In winter, mineral water at very low temperatures ah begins to crystallize and cannot ensure normal pumping of fluid through the lubrication system, as well as starting the drive without warming up. In summer, this engine oil liquefies at high temperatures outside the car and cannot form a stable protective oil film on the engine elements.

Unlike other fundamentals, mineral liquids no additives needed for normal operation most modern engines.

Synthetics and semi-synthetics differ from mineral water in the following characteristics:

Fluidity. Mineral water is too thick for use in modern engines.
Molecular structure. The heterogeneity of the molecular structure of mineral mixtures leads to a decrease in their resistance to crystallization and liquefaction.
Additives. In synthetics and semi-synthetics, additives are better; they do not break down at high temperatures overboard. In contrast, for mineral water, additives of natural origin are used, which burn out at high temperatures.
The difference in terms of replacement, synthetics changes much less frequently.
Mineral water forms more deposits during engine operation.

Among the advantages of mineral motor oil should be highlighted:

These fluids work best in high mileage engines. Unlike synthetics, which have great detergent properties, mineral mixtures do not lead to detachment of soot from drive units and do not cause clogging of the lubrication system and motor channels. Mineral water washes carbon deposits from internal elements motor gradually.
Mineral water, unlike synthetics and semi-synthetics, interacts less aggressively with the rubber surfaces of the lubrication system and drive units, and does not lead to their destruction.
Improves performance of worn power units. Mineral oils are quite thick, they are able to fill the increased gaps in the friction units of motors with high mileage.

Conclusion

Mineral motor oils in terms of viscosity characteristics lose to synthetic and semi-synthetic fluids. But there is power units in which only mineral water is possible, for example, only mineral oil has been poured into the engine for several years or the drive has a significant escape. In such situations, the use of synthetics or semi-synthetics is unacceptable due to the large amount of carbon deposits inside the motor.

When choosing mineral oil, consider the requirements of the car manufacturer, the type of engine, the base mixture that was previously poured into the engine.

With the advent of various types of oils, disputes do not stop about which oil is better to choose in the engine of your car. Each type of oil has many supporters, but often their arguments are based on myths, so choosing the type of oil in a car engine needs to be approached a little more thoroughly. Mineral or synthetic oil? Or maybe semi-synthetic? This article will show the differences between the types of motor oils, what is their difference and whether it is possible to mix lubricants of different composition.

Engine oil in the engine - purpose

The original purpose of motor oils is to remove heat from rubbing parts inside the engine, as well as, if possible, to remove metal particles that form during friction. By and large, nothing has changed for a long time, and on this moment these tasks are presented when choosing an oil. However, it is worth considering the fact that with the advent of semi-synthetic and synthetic oils on the market, motorists begin to actively argue about the temperature regime of the ambient air at which they can be used. A large number of lubricant manufacturers and their properly aligned marketing companies to attract new customers only exacerbate the matter.

Mineral engine oil

For the production of mineral oil, agricultural crops are used or it is obtained during the processing of fuel oil and the subsequent purification of processed products. Since this technology is quite simple and for many years people have successfully tried to simplify this process, this is due to low cost mineral lubricating oils. As positive effect from the use of mineral oil in a car engine can be distinguished high efficiency in use, hydrolytic stability and slight mechanical impact when interacting with moving parts of the engine. In addition, mineral oil can interfere with other identical and natural oils have an excellent anti-corrosion formation coefficient.

But all these positive properties mineral oils are often achieved at a comfortable temperature range 10 to 25 degrees Celsius. The use of mineral oils at low or high temperatures requires the use of various additives. But this is the obvious disadvantage of using mineral motor oils: at high temperatures, additives burn out, and at low temperatures, the use of mineral oils is difficult due to their high viscosity coefficient.

Semi-synthetic engine oil

Such an intermediate type of engine oil can be obtained by diluting mineral oil with synthetic oil. Experts recommend using proportions of 50% to 50% or 70% mineral to 30% synthetic motor oil.

Synthetic engine oil

The coolant for the engine is obtained by the synthesis of molecules. So during operation, synthetic oils show more qualitative indicators stability and are not so strongly affected by exposure to low temperatures. The choice of synthetic oil is desirable to be carried out according to individual parameters: the region of residence and the presence of high or low temperatures during the use of the car, the nature of driving and starting, etc. Of course, it is worth considering the fact that such oil cannot be found in nature unchanged, but it has become so firmly established in everyday life. modern life that people do not think about its origin. The price of synthetic oil is the most expensive of all the above materials, but in the presence of very low ambient temperatures, it is a necessity rather than a privilege.

The advantages of using synthetic petroleum products include:

Increased anti-friction properties.
There is practically no need to use additives, since the main part was added by the manufacturer at the production stage.
Lower evaporation coefficient before mineral oil products.
Use at low temperatures.

Advantages of various lubricant formulations over others

Synthetics and mineral composition - which oil is better: these oil products differ at the molecular level. The molecular structure of synthetics was achieved through long-term testing to achieve the required properties, and the molecular structure of mineral oil products was laid down by nature. If in some component synthetic oils are worse than mineral lubricants, then this is also over continuous work. But the fact is that mineral mixtures clean the engine continuously and with approximately the same efficiency, while synthetics, in turn, due to their viscosity, clean quickly enough. Because of this effect, oil filters and oil lines are literally clogged with particle deposits from the engine. In this case, with improper control of the elements oil system the effect of "oil starvation" and subsequent engine failure may occur.

Therefore, we can distinguish the main differences between the two main types of oils:

different molecular structure.
The different nature of the response of oils to changes in temperature, in this synthetics are much better than mineral ones.
Different fluidity of oils: due to exposure to low temperatures, mineral oil becomes thicker, synthetics are much more versatile in use.
Stability consists in the burnout of additives of mineral oil products, which leads to a change in the operation of the engine or its failure.

Mineral or synthetic oil? The answer will depend only on the car owner of a personal car.

Which oil is better: synthetic or semi-synthetic? What do the terms resistance and stability mean when using synthetics? This means that exposure to low or high temperatures practically does not reduce the viscosity, and hence the effectiveness of the oil for a long time. When choosing in favor semi-synthetic oil it should be noted that in some cases its use is more reasonable than synthetics. For example, with a large impressive engine mileage, synthetics can give high carbon monoxide, as well as when using a car with comfortable temperatures in the winter season - up to -20 degrees Celsius. However, the replacement this oil needs to be produced more often than synthetic.

In addition to the molecular structure, oil products for engine cooling are usually divided into seasonal use: summer, winter and multigrade oil. Summer oil, due to its viscosity, is reasonable to use up to 0 degrees Celsius. Otherwise, there is a high probability that the engine will not be able to start or will fail. Marking of summer oils: SAE 20, SAE 30 and so on up to 60. The designation of the numbers indicates the viscosity of the oil at operating temperature engine, the higher the number, the thicker the oil when heated.

Winter oils are marked from 0 to 25 units with the prefix W - winter (winter). Discreteness through 5 units. The minimum threshold for the temperature regime used is determined by subtracting 40 units from a given number. For example, for oil products marked 5 W, the minimum temperature at which the correct pumping of the oil system is ensured will be -35 degrees Celsius. But for winter oil products, it is also necessary to know such a selection criterion as crankability. To determine this parameter, 35 must be subtracted from the given number, while it is safe to say that for 10 W oil, the lower limit for the safe start of a car engine is 25 degrees Celsius.

All season oils. Lubricant marking is indicated by a combination of alphabetic and digital notation winter and summer oil. As an example, 5W - 30 can be deciphered as follows: winter marking 5 W and summer marking 30 indicates that safe launch engine can be produced at a minimum ambient temperature of -35 degrees Celsius and the maximum allowable viscosity with a working engine will be 30 units. What is the difference between 5W-30 and 5W-40? The whole difference lies in the fact that the first of the presented types of lubricants in summer period more than a season liquid consistency. Therefore, if in the region of residence most of the year is positive temperatures, then for the proper operation of the motor, it is necessary to purchase a lubricant with a higher viscosity. In winter, these oils will ensure uninterrupted engine start at -35 degrees Celsius. Viscosity table of motor oil classification:

small and useful advice on the choice of oil for a car from experts:

Before purchasing a lubricant for your car engine, you should carefully read the recommendations for using a particular type of oil directly from the manufacturer.
Storage of lubricants is allowed with a tightly closed container lid, which prevents air, moisture or other foreign objects from entering the used oil.
The operation of more expensive oils is not always smart choice, this can lead to a violation of the stability of the entire oil system.
Do not succumb to the tricks of sellers, and buy oil only hoping for their advice. It is necessary to understand that all lubricants, including mineral or synthetic oil, are produced using approximately the same technology. The whole difference lies in the quantity and quality of additives added.
An oil change must be carried out within the time specified by the manufacturer in terms of time or vehicle mileage. However, one should take into account the fact that worn engine oil should be changed a little earlier. This is due to the need to remove more friction products and much more severe operating conditions.
Always change oil when changing oil filter, this operation costs little money, but helps to ensure high-quality filtration of the lubricant.
Can you mix 2 different types lubricants directly in the engine? The unequivocal answer is no! This leads to the formation of an insoluble precipitate.
Carefully monitor the condition of the oil level in the engine, do not allow it to go beyond the upper or lower limits, which are marked on a special dipstick.
If synthetics are flooded in the engine (for example, 10W - 40 of a certain brand), then the best option in case of necessary addition, carry with you a small container of the same oil. However, it is allowed to add a lubricant from another manufacturer, but with the same marking.
Occasionally clean the oil system of a car engine using special means And a large number of oils. This allows you to completely renew the lubricant in the engine and completely remove metal wear products.
Before purchasing a lubricant for an engine, you need to study its expiration date on individual packaging. Tip: to prevent the purchase of low-quality fake oil it is wiser to buy it from official suppliers or trusted sellers in sealed metal packaging. This does not exclude the possibility of forgery, but reduces it to a minimum.

Conclusion.

Now many inexperienced motorists will be able to replenish their knowledge base on whether it is possible to mix and what is the difference between various types oils. Which oil is better to fill in your car can be determined based on your knowledge of the properties and markings of these lubricants, as well as the nature of behavior at different times of the year, and not on the advice of annoying sellers and television advertising. And also to determine the type of lubricant for cars with high mileage, because it is far from always reasonable to use expensive oil instead of a cheaper one, but effective in a particular case.