The yields corresponding to the amount of methanol used to produce biodiesel from used vegetable oil are summarized in Table 1.
Table 1 also shows that the yield increased from 86ml to 90ml by increasing the methanol concentration from 20% to 40%.
Further increase of methanol concentration from 40% to 50% produces a similar yield of 90ml biodiesel.
One can conclude that, the optimum concentration of methanol for this particularly case seems to be in region of 30-40 %, which produces a high yield (90ml) of biodiesel having reasonable glycerol settling rate.