Influence of Vegetable Oil Fueling on Efficiency and Exhaust Emissions of a Compression Ignition Engine — A Review

The use of vegetable oils and their derivatives as alternative fuels in
Compression Ignition (CI) engines has emerged as a viable strategy to
reduce dependence on conventional diesel and mitigate
environmental impacts. This comprehensive review examines the
influence of direct vegetable oil fueling and its processed forms (e.g.,
methyl esters) on engine performance metrics such as brake thermal
efficiency (BTE), brake specific fuel consumption (BSFC), and key
exhaust emissions including NOx, CO, HC, and particulate matter
(PM). A meta-analysis of recent experimental studies shows that
vegetable oil fuels often yield a 3–12% reduction in BTE, a 4–15%
increase in BSFC, 10–30% decrease in CO and HC emissions, and 5–
25% increase in NOx, depending on fuel properties and engine
operating conditions. The review contextualizes these findings with respect to combustion characteristics, fuel physicochemical
properties, and engine modifications. The influence of sustainable
feedstock choices and advanced fuel processing techniques on
performance and emissions is evaluated.