Purchase Guide


API: is an abbreviation for American petrolume institute.another kind of standard for determination of engine oils quality level.for gasoline and diesel engines API has unique symbol.S For gasoline engines and C stands for diesel Cr engines .therefor if an engine oil happens to be suitable for gasoline engine it will start as API S and engine oils suitable for diesel engines starts with API C.

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SAE: this standard is an abbreviation of (society of automative engineers) .this standard is composed of numbers between 0 to 60. and in some cases the letter W can be seen in it.the number zero in this standard indicates minimum amount of viscosity and depicts an oil which can be easily flow but by going near to 60 the amount of viscosity arises and SAE 60 shows kind of engine oil with very high which means it is hard to flow. The letter W stands for minimum amount of viscosity is winters cold weather.

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Engine oil purity level based on production process.
Another important factor in choosing a kind of engine oil is the purity factor of engine oil production.
The production process of producing any engine oil differs from another.
Engine oils are divided to three types based on their production process:

  • Mineral engine oil (Mineral)
  • Semi synthetic engine oil
  • Fully synthetic engine oil
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Engine Oil Purchase Guide

Certainly, it has happened to you to go to a mechanic for changing engine oil and watching different brands on the shelves and ask yourself that which one is suitable for my car?

Maybe you ask your mechanic for help to see what choices you have which is quiet logical but does your mechanic know about your cars performance or about what climate your car will be used in? Therefore, it is better for you to be aware of what kind of engine oil youre buying before any problem happens to your car engine with a little time buy the most suitable engine oil for your car.
Of course, you have to pay attention to this matter that recently car producers with assessing production process and its standards propose engine suitable oils from certain large manufacturers in contract with them according to necessary standards of your vehicle.therefor you can look up to owners manual of your car and find the type and brand of the engine oil suitable for your car.
In this article we have tried to mention essential factors for choosing engine oil to make you be able to choose and buy your engine oil with adequate information and awareness

Significant factors in choosing engine oils

API Factor :

The American petroleum institute or briefly API indicate engine oil quality.this index is visible on engine oils lable with two English letters.first letter illustrates engine oil type (diesel or gasoline) and second letter indicates engine oil quality starting in aplabetical order.

Old indexes are SA/SB/SC/SD/SE/SF the engine oils with this standards have low quality and their usage in modern cars have been antiquated.

To choose quality index of engine oil based on what has been written in your cars owners manual it is better to use the same quality or higher qualities and never use engine oils with lower quality. It is obvious that engine oils produced with higher levels of quality have capabilities that are more technical, this matter does not have any relation with your cars production date .engine oils with SM, and Sn quality indexes are the best for your car

Quality index based on API

In addition, you can use engine oils with SN quality instead of SM because the quality of it is higher than SM engine oil and not only is it not going to For example if it is mentioned in owners manual that you must use engine oil with SN quality.we advice that you do not use engine oil with lower rankso an engine oil SM index is not appropriate for your vehicle.The diagram below indicates that with passage of time and advancement in technology how this index has chaged from SA to SN.so it is much better to pay attention to this factor when purchasing engine oil and use high quality enigine oils for your car.

Engine Oil Density Factor SAE :

Another factor, which has essential role in determination of engine oil, is the type of engine oil regarding its viscosity.it means that how much should engine oils density be in order to have best performance according to weather conditions and engine performance Society of automative engineers or briefly SAE have designated a particular standard to determine engine oils viscosity which eases the process of diagnosing engine oil and you can easily purchase suitable engine oil for your vehicle of course it is important to consider that with recent advancements in technology multi grade engine oils have entered market which demonstrate effective performance in various temperatures If you look precisely at engine, oils this index is available in the following forms :

(SAE: 10W-40, 05W-40, 05W-30, 10W-30, 20W-50, 0W-20, …)

First letter before letter W demonstrates engine oils viscosity in low temperature (winter), the lesser this number is the more diluted engine oil becomes. This number plays an essential role in first start in cold days of winter. Because,for lubricating engine in this situation engine oil must be far more diluted in order for lubrication to happen correctly, for cold weather in winter may cause engine oil to become denser which brings about damage to engine and cause corrosion of segments as a result of wrong lubrication Therefore this number reduces engine oil will be extra diluted and ensures you that in first start all engine parts will be lubricated and engine starts working effortlessly The bigger the number the denser the engine oil.
for example if your are living in a city like Ahwaz in which the temperature could rise up to +40 centigrade degree it is better to choose an engine oil, which does not loose its lubrication features according to weather and engines heat It means that its density has to be adequate because engine oil might become completely diluted in this condition and therefor loose, its performance.so it is better to pay attention to the table in the following, which indicates engine oils temperature range, based on viscosity

For example, W-40 10 engine oil is applicable according to table in temperature range of -30 to +40- centigrade degree; therefore using diagram above you can easily choose engine oil that matches weather conditions that you are living in. For example Tehran and its vicinity, temperature in summer is in range of -10 to +40- centigrade degree. Therefor, according to this temperature, that type of engine oil is suitable which has high viscosity in high temperature .
as a result utilization of engine oils with viscosity index 15W40 or 10 W-40 is suggested in this temperature range For cold climates, it is better to use engine oils, which are more thin and diluted or in other words have lower viscosity so in a cold day, the motor will be able to start without difficulty and no damage will occur to engine. If viscosity happens to be high engine oil might not lubricate properly in first start and that brings about damage to your car engine.
Ardebil, Shahrekord, Tabriz, Hamedan, Sanandaj are of cities in which engine oils with lower viscosity is more advised.for example engine oils such as W-20, 0W-30,0W-40, 5W-30,05W-40….. Are appropriate for these cities

For cities located in warm areas of the country, those engine oils are suitable that have high viscosity For example for cities like Bandar abbas, Sistan balouchestan, Ahwaz, Isfahan, Kerman, and …. It is better to use engine oils that have high viscosity and density in high tempreture. For instance, engine oils such as W-50, 10W-40, 20W-50, and 15W-50… are wise choise for these cities. Therefore, it is better to pay attention to this significant factor before purchasing your engine oil

Engine Oil Purity Factor Based on Production Process :

Another factor important in choosing an engine oil is engine oils purity factor.production process of every type of engine oil differs from one another. The produced engine oils can be devided to three types based on their production process :

  • Mineral engine oil:

    Maybe in a way it can be said that this kind of engine oil producing process, is the first in which there is no optimization operation In fact, this engine oil has been produced based on crude oil and it enters markets without any correction in chemical structure This engine oil is specifically for old and classic cars.despite the fact that this its price is low but because of its simple structure, the time between oil changes is shorter.

  • Semi synthetic engine oil:

    This engine oil is a combination of synthetic and mineral engine oils.synthetic engine oils are produced in laboratory and their chemical structure in modified, which makes them have higher resistance and performance. this type of engine oil is applicable in current cars which are not expensive and it is suitable for cars like Peugeot 206, Peugeot 405, Peugeot Pars, Samand, Tiba, MVM, and ….

  • Fully synthetic engine oil:

    This engine oil has been produced based on latest technology and every impurity of has been totally removed from it and besides its chemical structure is reinforced in a way that has enhanced lubrication and resistance comparing to other engine oils. Fully synthetic engine oils are specially made for cars with high tech engines.for example Benz, BMW, Toyota, Honda, Hyundai and KIA ought to use this type of engine oil.the price of this engine oil is higher than mineral and semi synthetic engine oils.
    Though fully synthetic engine oils have better performance in terms of functioning but nonetheless this type of engine oil is not suitable for certain kinds of cars or there is no necessity for consuming it because it only makes your expenses go higher.
    Considering the above mentioned. Perhaps from now on you become a little more sensitive when choosing engine oil and choose precisely the suitable engine oil for your car.purchasing appropriate and compatible engine oil for your car not only increases engine efficiency but also its longevity will be improved .


In selecting and purchasing an engine oil, it is better for you to refer to your cars user manual and then consider other factors although it is possible that for instance your cars users manual suggests a particular engine oil which might be due to producers countries weather condition or based on a temprate climate.but if you live in hot or cold climates it is better to be more sensitive to weather conditions when it comes to purchasing engine oil.

Frequently Asked Questions

Is it right to combine mineral engine oils with synthetics or not?

Assume that you are in travel and you understand that the volume of your engine oil is less than the usual amount and inevitably, you have to add some engine oil but maybe you will not be able to find the exact oil in your vehicles tank

For example, you have used synthetic engine oil but all you have at that moment is mineral engine oil

According to recent studies accomplished at Mobile one company which is one the pioneers in production of engine oils, adding these two oils together would not make any issues because they are compatible to each other.

In fact, most of produced engine oils are a combination of mineral and synthetic engine oils and adding them to each other will not create any problem to your engine. However, it is much better to change in advance because for existing different complementary they might have interference and may not work efficiently.

If you’re supposed to add engine oil, we propose that you use the same brand and grade, which is already in the tank. Because different brands use their own particular complementary and they might not be compatible when combining to engine oils from another brand.

If your engine oils grade is W-40 it is better to use the same grade otherwise you can use a similar grade from the same brand in the tank.

It is better for you to write your engine oils information into a notebook to use it in case of need.

When is the best time to change engine oil?

Changing engine oil depends on the type of engine oil (mineral, Synthetic, Fully synthetic) existing in engine oil tank, your style of driving, and information available in the car notebook (periodic services).

However, the expiry time of every engine oil is mentioned on every bottle which can be refereed to, if your car has been slept for a long time in the parking changing engine oil is suggested.

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