The effect of various feedstock alkyl esters on fuel lubrication and properties

This study examined how different feedstocks and alcohol types affect biodiesel properties and lubrication performance. Five feedstocks (palm, sunflower, rice bran, pork lard, and rapeseed) were transesterified using methanol and ethanol, followed by comprehensive analysis of their properties and lubricity characteristics according to ASTM standards and ISO 12156–1. Gas chromatography revealed distinct fatty acid profiles across feedstocks, with unsaturated fatty acids ranging from 53.4 % to 91.1 %. Ethyl esters demonstrated 5.47–16.65 % higher kinematic viscosity but improved lubrication properties compared to methyl esters, showing up to 13.9 % smaller wear scar diameters and 4–25 % shallower wear depths in high-frequency reciprocating rig (HFRR) tests. Notably, biodiesels from feedstocks with higher polyunsaturated fatty acid content, particularly sunflower (58.7 %), exhibited superior lubricity with wear scar diameters of 150–156.5 μm. While ethyl esters showed better lubrication, methyl esters demonstrated 0.42–0.80 % higher density and 1.92–5.88 % higher heating values. Surface analysis at 3000x and 10000x magnification revealed similar wear patterns across all biodiesel samples, suggesting that ester type has minimal impact on metallic structure formation.