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This paper aims to explore the effects of mineral diesel fuel carbon soot (MCS) and biodiesel carbon soot (BCS) on the lubrication of polyalphaolefin (PAO) and diesel fuels.

Two styles of carbon soot were prepared from the natural combustion of mineral diesel fuel oil (MDO) and biodiesel oil (BDO). Tribological tests were conducted on a high-frequency reciprocating rig. Friction surfaces were characterized using three-dimensional laser scanning confocal microscopy and Raman spectroscopy.

The addition of MCS and BCS to PAO could reduce friction in most cases. MCS had a negligible effect on the wear for contents not exceeding 1.0 per cent. By contrast, BCS exhibited a considerable negative influence on the wear resistance even at low contents. For diesel fuels, MCS reduced both friction and wear, whereas BCS substantially deteriorated the lubrication of BDO. MCS formed a Fe₃O₄/C composite lubricating film on the friction surface. BCS also entered the contact region, but it did not form an effective Fe₃O₄/C composite lubricating film.

This work compared MDO and BDO from a different perspective, i.e. the effects of their combustion carbon soot on the lubrication of lubricating oil and fuel oil. The significant negative effect of BCS on the lubrication of lubricating oil and BDO is a problem that could occur in the industrial application of BDO.

Environmentally adapted lubricants (EALs) have been a slowly growing segment of the lubricants business since the early 1970s. The evolution of environmental thinking has led to the change of focus, from biodegradability to renewability. In the future, the focus will be more on fuel economy and lower emissions. Technical development drivers include the availability of suitable base fluids and additives for lubricants formulation and the adaptation of technical standards, OEM specifications and eco‐labels. Important non‐technical development drivers include environmental management tools and eco auditing. Environmental policy, and procurement guidelines for cities and government organizations, clearly has a large impact. EALs have been repeatedly heralded as one of the few future growth segments of the lubricants business, hence the relatively large increase in R&D activity over the last decade. In sales terms, growth has been slow, limited by high cost and several other factors. For a good future development, both technical and political hurdles must be overcome.