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Both carbon blacks and carbon nano-onions nanoparticles have a spheroidal shape and a nested structure. They can be used to simulate the presence of soots in used engine oils. When added to fully formulated fresh engines oils, these two kinds of particles behave very differently. Carbon black particles are highly abrasive causing a lot of wear of steel surfaces and friction increases. At the opposite, the addition of carbon onions in lubricant leads to a reduction of both friction and wear compared to pure base oil. This shows that there is an opportunity to control wear in engines by changing the structure of soots during the combustion process.

Nitrogen compounds present in mineral base oils at low concentrations are known to accelerate oil oxidation and to reduce the useful lifetime of formulated lubricants. Both Partial Least Squares and Neural Network analyses were employed to establish correlations between base oil composition and performance in industry standard thermal stability and oxidation tests. These correlations show that the “basic nitrogen” (BN) content of a base oil is a very important compositional feature determining its ultimate performance in a formulated lubricant which may be especially important for API Group II and III base oils that are relatively free of other pro-oxidants and naturally occurring, sulfur-containing antioxidants. The effect of BN species was also studied using model nitrogen compounds and it was confirmed that the pro-oxidant effect appears only in “basic” nitrogen containing molecules involving pyridine and quinoline derivatives.