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Then let’s talk about the types of additives.
Viscosity index improver: ethylene/propylene copolymer, polymethacrylate, hydrogenated styrene/diene copolymer, mixed polymer. By means of the polymer coils that expand and contract with temperature changes, the viscosity of the base oil decreases at high temperatures is compensated.
Antifreeze agent: Poly(methyl methacrylate), poly(α-olefin), vinyl acetate/butadiene maleate copolymer, alkyl naphthalene. It modifies the shape and quantity of wax crystals, inhibits the formation of crystal networks, and maintains the flow of the oil product.
Antifoaming agent: Methyl silicone oil, polyacrylate. It reduces surface tension, accelerates the disintegration of foam, and prevents the formation of persistent foam in the oil.
The table below, though not very precise, can basically illustrate the correspondence between the types of additives and the types of oil products they are applied to.
Application of additives (✓ Required; △ Sometimes used)

	clearing agent	dispersant	Antioxidant Anticorrosive agent	VII	PPD	antioxygen	anti-wear reagent at extreme pressure	antirust agent	anti-foaming agent
Gasoline engine oil Diesel engine oil Marine cylinder oil Two-stroke oil	√ √ √ √	√ √ √ √	√ √ △	△ △	√ √ △	√ √ √	√ √	√ √	√ √ √
Gear oil Ordinary turbine oil Anti-wear turbine oil			△	△ △	√	√ √ √	√ √	√ √ √	√ √ √
Ordinary hydraulic oil Anti-wear hydraulic oil Aircraft hydraulic oil				△ √	√ √ √	√ √ √	√	√ √ √	√ √ √
spindle oil					√		√
refrigerating machine oil					√
compressor oil					√		√	√
oil for electrical appliances				△	√

There is a concept that I wonder if everyone is familiar with: Among the additives for lubricants, approximately 75% are used in engine lubricants.
Overall, dispersants can be regarded as the largest category of additives; the development speed of antioxidant varieties and production volumes is the fastest; and special additives have the highest value (profit).
There is another trend: the usage of non-ashless antioxidants in diesel engine oil has exceeded that of ZDDP (dialkyl disulfide zinc phosphate) as the grade of the oil increases.
In the research and development of lubricant formulas, the first step is to precisely select corresponding additives based on the various properties of the oil to meet the requirements for passing various standard tests. Then, a balance is made among the additives to form the final formula. Subsequently, we need to review it again, unraveling the details, and summarizing the characteristics of the entire formula. For example, for engine oil, generally speaking, gasoline engine oil emphasizes low-temperature dispersibility, while diesel engine oil focuses on high-temperature cleanliness. However, this is not always the case; there are exceptions in special circumstances.