The nanostructure of soot-in-oil particles and agglomerates from an automotive diesel engine

► Soot-in-oil particles extracted from used lubricating oil have been investigated. ► Soot in oil shows modest branching with average length of 121.7 nm and 81.7 nm in width. ► 54% Of the soot analysed existed in long-chain agglomerates (L/W>2.5). ► Soot spherical primary particles of 10-30 nm form the agglomerates. ► Primary particles exhibit a core-shell structure (10-21 nm core; 4-12 nm shell).