How should ashless dispersants be used?

How should ashless dispersants be used?

Currently, succinimide based on polyamines is the mainstream ashless dispersant, accounting for over 80% of total ashless dispersant usage. Its chemical structure consists of a lipophilic group, a polar group, and a linking part. This structure easily forms micelles in lubricating oil, ensuring strong solubilization of initial oxidation products in liquid form and excellent colloidal dispersion of solid particles such as carbon deposits and soot. This effectively ensures the low-temperature dispersion performance of internal combustion engine oils, particularly effectively solving the low-temperature sludge problem in gasoline engine oils.

Gasoline engine oils containing ashless dispersants show reduced sludge in the crankcase after prolonged operation and oil changes. It also improves the dispersion and solubilization of soot and lubricating oil oxidation products generated at high temperatures. Especially when combined with metal detergents, it has a synergistic effect, improving the quality of the lubricating oil while reducing the amount of additives required.

Since the main functions of ashless dispersants in oils are dispersion and solubilization, an addition of 1-10% to modern automotive engine oils is sufficient to effectively control the smoke point of diesel engine oils.

Railway locomotive oils require good alkalinity reserves and high dispersibility, necessitating the addition of ashless dispersants. For medium-speed cylindrical piston engine oils, a lower addition of 2-4% is preferred to achieve good dispersion. While traditionally, ashless dispersants are not added to marine cylinder oils, laboratory studies have found that adding them not only improves the detergency and dispersibility of marine cylinder oils but also significantly reduces the amount of highly alkaline additives required, lowering costs. Therefore, they are increasingly being used in the production of marine cylinder oils.

Two-stroke gasoline engine oils involve the mixing and combustion of lubricating oil and fuel oil. Excessive metal detergents and antioxidants can easily lead to wear and ring adhesion. Using special ashless dispersants or a combination of detergents can prevent these phenomena.

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