A metal-free polymeric additive, typically a polyisobutylene succinimide, with a polar head that grabs contaminant particles and an oil-soluble tail that keeps them floating. Dispersants stop soot from clumping into sludge that plugs filters and oil passages, and they are usually the largest single component of an engine oil additive package. Like detergents they hold water in emulsion, so turbine and circulating oils keep them to a minimum.
Soot's at 3 percent but the pan is clean, the dispersant is still holding it all in suspension.
Also heard as
- ashless dispersant
Related terms
Detergent
Metal-based additive that keeps hot engine parts clean and neutralizes acids from combustion.
Varnish
Thin, sticky, amber-to-brown deposit from degraded oil that coats valves, bearings and coolers.
Additive package
Pre-blended mix of performance chemicals that a blender adds to base oil to make a finished lubricant.
Demulsibility
How quickly an oil sheds water and settles into clean layers after being churned with it.