Optimal fuel selection in diesel-biodiesel-ethanol-methanol blends: a comparative analysis of TOPSIS and VIKOR methods under different weighting scenarios

ALTINKURT M. D., ESEN D. Ö., Shabaneh S. A. Y. A., Soyler H.

ENVIRONMENTAL RESEARCH COMMUNICATIONS, vol.8, no.7, 2026 (SCI-Expanded)

Abstract

Increasing the proportion of renewable low-carbon alcohols such as bioethanol and methanol in fuel blends is crucial for achieving sustainable and carbon-neutral internal combustion engines. In this study, combustion, performance, and emission characteristics of diesel-biodiesel-alcohol blends with varying bioethanol and methanol ratios were experimentally investigated on a 4-cylinder 1.9 l turbocharged common-rail direct injection light-duty diesel engine. Seven different fuel blends, including pure diesel as reference and six alternative blends, were tested at constant engine speed (1750 rpm) and four engine loads (40-160 Nm). The optimal fuel blends were determined using Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) and VlseKriterijumska Optimizacija I Kompromisno Resenje (VIKOR) multi-criteria decision-making (MCDM) methods. The results showed that the D50-B30-E5-M15 blend (50% diesel, 30% biodiesel, 5% ethanol, 15% methanol) achieved the highest brake thermal efficiency (BTE) of 32.933%, representing a 6.63% improvement compared to diesel (30.884%). This blend also significantly reduced unregulated emissions, including 65.8% reduction in NH3, 22.1% reduction in C2H4, and 30.2% reduction in total hydrocarbons emissions. However, emission trends varied depending on blend composition. MCDM analysis revealed methodological differences between ranking approaches. TOPSIS consistently ranked D50-B30-E5-M15 as the best alternative under equal-weight, performance-oriented, and emission-oriented scenarios, while VIKOR suggested different optimal blends depending on weighting priorities. A comprehensive scenario-based sensitivity analysis demonstrated that the D50-B30-E5-M15 blend consistently maintains its top-ranking position across various weighting strategies, confirming the robustness and reliability of the selection. Overall, this study provides a systematic evaluation of quaternary diesel-biodiesel-ethanol-methanol blends and demonstrates their potential as sustainable low-carbon fuel alternatives.