Tribological, viscous, and thermal properties of low-viscosity <i>Scenedesmus</i> microalgae oil as a new green and sustainable additive for vehicle lubricants

The use of biodegradable oils as additives to produce green lubricants with low viscosity is a current trend for meeting worldwide environmental care demands and energy savings in vehicles. Most biodegradable oils come from oil-rich crops, mainly edible vegetable oils, which are not sustainable sources for achieving the massive production of biofuels or biolubricants without altering the food chain supply. Recently, microalgal oils have emerged as sustainable alternatives for producing high-value amphipathic lipids/oils for potential lubricant production. However, the lubrication performance of these oils, mainly pilot-scale produced oils, is still far from being well-established. This study aimed to assess the tribological, viscous, and thermal stability properties of a pilot-scale produced Scenedesmus sp. microalgae oil ( Scenedesmus oil) as a potential additive for producing low-viscosity biolubricants. Scenedesmus oil was added at low concentrations to a low-viscosity mineral oil and its effect was evaluated by standard four-ball tests. The viscosity of Scenedesmus oil was found to be much lower than that of mineral oil. Notwithstanding, neat Scenedesmus oil and its blends presented better lubricity, though lower thermal stability than neat mineral oil, both of which were related to its FAMEs content. Overall, Scenedesmus oil was found to be a promising lubricating additive for the sustainable production of low-viscosity biolubricants for applications operating below 137 °C.