What's the difference between dispersants and detergents in lubricants?

Detergents and dispersants are all Deposit Control Additives in the lubricants. The combination of detergent and dispersant can complement each other's performance and achieve a synergistic effect.

Modern engine oils are formulated by compounding high TBN detergents with ash-free dispersants such as Ashless Dispersant Polyisobutylene Succinimide in appropriate proportions.

What is the difference between lubricant dispersants and lubricant detergents?

Dispersants differ from detergents in three significant ways:

1. Dispersants are metal-free, but detergents contain metals, such as magnesium, calcium,
and sometimes barium. This means that when combustion the detergents will lead to ash formation and dispersants will not.

2. Dispersants have little or no acid-neutralizing ability, but detergents do.

3. Dispersants are much higher in molecular weight, approximately 4–15 times higher, than
the organic portion (soap) of the detergent. Because of this, dispersants are more effective
in fulfilling the suspending and cleaning functions than detergents.