Base oil type

I would like to introduce the types and characteristics of base oils, as well as my own considerations and thoughts.
First of all, there is a standard called API Base Stock Group, which I will explain roughly.
Group 1
Refined mineral oil with relatively high impurities such as sulfur and nitrogen compounds.
Group 2
Refined mineral oil with medium level of impurities
Group 3
Refined mineral oil with low level of impurities; highly hydrogenated and refined oils are also in this category, and are described as semi-synthetic or fully synthetic.
Group 4
PAO and polyalphaolefin are in this group.
Group 5
Other synthetic oils, such as esters and alkylnaphthalenes, belong to this group.
Group 1 to 2
Mineral oils are naturally mined and their raw materials are subject to variations, so some are good and some are not so good.
Impurities may temporarily improve the lubricating performance and stability of the oil. However, impurities are removed and synthetic lubricants and stabilizers are added for higher performance because they will eventually accelerate oxidation and polymerization.
Group 3
Refined mineral oil is also included in Group 3 if it meets the criteria, but there is also hydrocracking oil hydrocracking oil, which is a hydrogenated, refined, processed oil that is reformed and refined by cracking and resynthesizing mineral oil as a raw material. Refined mineral oil and synthetic oil are mixed in Group 3, and although it is complicated, most inexpensive oils that are labeled "fully synthetic" are this type.
Personally, I think this synthetic base oil has the best price/performance ratio and is the easiest oil to use.
Group 4
PAO polyalphaolefins are made by polymerizing olefins and have uniform molecular composition and physical properties. They have a strong molecular structure with good viscosity characteristics and little change in viscosity.
They also have better sharpness than other oils and less loss due to dynamic resistance.
Group 5
Other synthetic oils are in this category.
Commonly used base oils are esters and alkylnaphthalenes.
It is appropriate to use them as additives for engine oil.
Ester is a substance consisting of an ester bonded to an acid and an alcohol. The constituent materials include inorganic acids such as hydrochloric sulfate, phosphoric acid, and boric acid, organic acids including fatty acids, and alcohols, including methyl, ethyl, oily, and wax-like higher alcohols, and phenols including cyclic molecules. There are countless types of esters, including those that are actually used in manufacturing.
The advantage of esters is that they chemically adsorb on metals, forming an oil film that is resistant to high temperatures. The disadvantages are that they are difficult to mix and easily separate, compete for adsorption, and interfere with other lubricating components.
It is better to use such esters as additives because they are relatively easy to manufacture and inexpensive.
There are complex esters, in which a different ester structure is introduced into each chain to achieve high performance, but they are very expensive and their distribution is not stable.
AN (alkylnaphthalene) is a naphthalene molecule with two benzene rings attached to a linear alkyl chain. The longer the alkyl chain, the higher the viscosity, and the benzene ring is highly stable, Alkylnaphthalenes also have these properties (although not all molecules with benzene rings have these properties, of course, due to a variety of factors).
AN, like esters, is said to chemically adsorb to metals and form oil films. (I think the adsorption strength of AN is generally weaker than that of esters, although it depends on the type of ester.)
However, AN does not cause competition for adsorption (mild?) and does not interfere with other lubricating components. AN does not interfere with other lubricating components, in fact, it seems to work in the direction of helping them.
AN is heat resistant, oxidation resistant, has an anti-degradation effect on other base oils, has good lubricity, and is a true panacea that increases the effectiveness of other additives, lubricating ingredients, and antioxidants.
It is also good for lubrication and improves the effects of other additives, lubricating ingredients, and antioxidants.

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