Multiscale Modeling Approach to Understand Mechanism of Deposit Control by Sulfonate-Based Lubricant Detergents

Protecting the material surfaces from deposits and insoluble
sludge
particles extends the engine life and reduces waste. Lubricant detergents
in engine oils are essential additive technologies that prevent deposit
formation in internal combustion engines. In this study, the effect
of sulfonate detergent on deposit formation in a passenger car engine
is investigated with experimental and multiscale molecular modeling
methods to present a unified approach. First principles density-functional
theory calculations, statistical sampling methods, all-atom molecular
dynamics simulations, and coarse-grained simulations are examined
to elucidate deposit control mechanism of sulfonate detergents. Analysis
of the results reveals that sludge particles in the drain oil are
similar in structure to piston deposits, and they might be the precursors
of the piston deposits. Main factor for controlling the sludge particle
deposition is the prevention of their colloidal aggregation at the
microscale in the base oil matrix. Aggregation can be mitigated by
the intercalation of detergent polar groups between the particles.
This is followed by the extension of hydrophobic tails into the oil
phase, which decreases further aggregation via formation of a repulsive
layer.