\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Ref.**} & \multirow{2}{*}{**Year**} & \multirow{2}{*}{\begin{tabular}{c} **Engine** \\ **Characteristics** \\ \end{tabular} } & \multirow{2}{*}{\
\begin{tabular}{c} **Operating** \\ **Conditions** \\ \end{tabular} } & \multirow{2}{*}{**Fuel Type**} & \multicolumn{2}{c}{**Energy**} & \multirow{2}{*}{
\begin{tabular}{c} **Energy** \\ **Efficiency (\%)** \\ \end{tabular} } & \multirow{2}{*}{**Outcomes**} \\ \hline
[26] & 2016 & 1-cylinder & 12 different speeds & & 27.18–31.42 @ & 25.37–29.34 @ & \(\uparrow\) speed \(\downarrow\) efficiency \\  & 4 stroke & (1000–3000 rpm) & Diesel & 1400 rpm & 1400 rpm & \(\eta_{\text{ diesel}}>\eta_{\text{biench}}\) \\  & Antor 3 LD510 & Full load & D75-92/B10-20/E5 & 24.13–27.62 @ & 22.53–25.82 @ & \(\psi_{\text{ diesel}}>\psi_{\text{biench}}\) \\  & & & & 2800 rpm & 280 rpm & \(\psi_{\text{ diesel}}>\psi_{\text{biench}}\) \\ \hline
[29] & 2016 & 4-cylinders & & & 25.21–32.88 @ & \\  & 4 stroke & 5 speeds & Diesel & 40\% load & \(\uparrow\) speed \(\downarrow\) efficiency \\  & OM 314 Euro II & & 5 loads & D50-78/B0-40/E0-16 & 31.68–24.20 @ & \(\uparrow\) load \(\uparrow\) efficiency \\  & & & & 80\% load & \\ \hline
[30] & 2017 & 1-cylinder & 1500 rpm & & 23.49–27.05 @ & 20.91–24.49 @ \\  & 4 stroke & 6 loads & D30-45/B50/E5-20 & 25.33–32.19 @ & 23.29–29.32 @ & \(\uparrow\) load \(\uparrow\) efficiency \\  & Kirloskar TV-1 & (20–120\%) & & 100\% load & 100\% load & \(\psi_{\text{D35/E15/B50}}>\psi_{\text{ diesel}}\) \\ \hline
[31] & 2019 & 4-cylinders & 1600 rpm & &
\begin{tabular}{c} Diesel \\ D41-78/B17-49/E5- \\ 10 \\ \end{tabular} & 25.82–27.08 @ & n/a & \(\eta_{\text{ diesel}}>\eta_{\text{biench}}\) \\ \hline
[32] & 2019 & 1-cylinder & 1500 rpm &
\begin{tabular}{c} Diesel \\ D90-98/B1.5- \\ 7.5/E0.5-2.5 \\ \end{tabular} & 40\% load & 21.45–28.21 @ & \(\uparrow\) load \(\uparrow\) efficiency \\  & & 5 loads & 22.73–22.77 @ & full load & \(\psi_{\text{D00/B7/E5/E5/E5}}>\psi_{\text{ diesel}}\) \\  & & & & full load & \(\psi_{\text{D00/B7/E5/E5/E5}}>\psi_{\text{ diesel}}\) \\ \hline
[33] & 2020 & 6-cylinders & 1450 rpm & & 14.65–15.05 @ & 13.70–14.08 @ \\  & 4 stroke & 5 loads & GTL & 3\% load & 3\% load & \(\uparrow\) load \(\uparrow\) efficiency \\  & Scania DC 1102 & (3–92\%) & GTL & 3\% load & 3\% load & \(\psi_{\text{GTL}25/B5}>\psi_{\text{GTL}}\) \\  & & & 439.39–45.27 @ & 41.12–41.65 @ & \(\psi_{\text{GTL}25/B5}>\psi_{\text{GTL}}\) \\  & & & & 92\% load & 92\% load & \(\psi_{\text{GTL}25/B5}>\psi_{\text{GTL}}\) \\ \hline
[34] & 2020 & 1-cylinder & & 219–220 @ & \\  & 4 stroke & 1900 rpm & Diesel & 5.71 kW & n/a & \(\uparrow\) load \(\uparrow\) efficiency \\  & NSB-8.18 & 2 loads & D82/B10/E8 & 22.6–22.9 @ & \(\eta_{\text{ diesel}}>\eta_{\text{D82/B10/E8}}\) \\  & & & & 7.43 kW & \\ \hline
[27] & 2020 & 1-cylinder & 2 speeds & & 30.17–31.92 @ & 28.13–29.77 @ \\  & 4 stroke & Full load & D60-75/B20/But5-20 & 1400 rpm & 1400 rpm & \(\uparrow\) speed \(\downarrow\) efficiency \\  & & & & 26.91–27.83 @ & 25.03–25.96 @ \\  & & & & 2800 rpm & 280 rpm & \(\psi_{\text{ diesel}}>\psi_{\text{biench}}\) \\ \hline \hline \end{tabular} n/a: not available, D: diesel fuel, B: biodiesel fuel, E: ethanol fuel, GTL fuel, But: butanol fuel, FTD: Fischer-Tropsch diesel fuel.  
\end{table} 
Table 1: Summary of the energy and exergy results from other investigations.