Thermal barrier coatings have been shown to be effective at reducing particulate emissions from diesel engines. Prior work by the authors has demonstrated a significant decrease in particulate emissions from a thermal barrier coated, single-cylinder, indirect injection (IDI) diesel engine, primarily through reduction of the volatile (VOF) and soluble (SOF) fraction of the particulate. Most of this prior work relied on conventional, commercially available, petroleum-based lubricants. Recently, the authors demonstrated additional particulate emissions reductions when a high oleic sunflower-based lubricant was used instead of a conventional petroleum-based lubricant. This paper concerns the manner in which the particulate was reduced, and reports on the changes in particulate composition and morphology between the two lubricants. Composition was examined quantitatively through thermal analysis of the particulate from a single-cylinder IDI diesel engine. Morphology was examined qualitatively by optical microscopy of the particulate collected onto Pallflex filters.