Effect of biodiesel on the autoxidation of lubricant base fluids

The effect of low concentrations of methyl linoleate on the autoxidation of squalane (2, 6, 10, 15, 19, 23 hexamethyltetracosane) was investigated at temperatures 100 to 170 °C as a chemical model of the effect of biodiesel on the degradation of hydrocarbon lubricants during use. Below 158 ± 5 °C, methyl linoleate behaves as a pro-oxidant, whilst above 158 °C, it inhibits alkane autoxidation. This change of mechanism is consistent with the addition of oxygen molecules to doubly allylic carbon centred radicals formed by hydrogen abstraction from methyl linoleate becoming reversible above 158 °C.