▁b iod ies el ▁made ▁from ▁so y bean ▁oil ▁is ▁between ▁ 4 . 2 ▁and ▁ 4 . 6 ▁c St ▁The ▁vis cos ity ▁of ▁dies el ▁must ▁be ▁high ▁enough ▁to ▁provide ▁sufficient ▁lub ric ation ▁for ▁the ▁engine ▁parts ▁but ▁low ▁enough ▁to ▁flow ▁at ▁oper ational ▁temperature . ▁High ▁vis cos ity ▁can ▁plug ▁the ▁fuel ▁filter ▁and ▁injection ▁system ▁in ▁engines . ▁ ▁Veg et able ▁oil ▁is ▁composed ▁of ▁lip ids ▁with ▁long ▁ch ains ▁of ▁hydro car b ons , ▁to ▁reduce ▁its ▁vis cos ity ▁the ▁lip ids ▁are ▁broken ▁down ▁into ▁smaller ▁mole cules ▁of ▁est ers . ▁This ▁is ▁done ▁by ▁converting ▁veget able ▁oil ▁and ▁animal ▁f ats ▁into ▁alk yl ▁est ers ▁using ▁trans ester ification ▁to ▁reduce ▁their ▁vis cos ity ▁Nevertheless , ▁b iod ies el ▁vis cos ity ▁remains ▁higher ▁than ▁that ▁of ▁dies el , ▁and ▁the ▁engine ▁may ▁not ▁be ▁able ▁to ▁use ▁the ▁fuel ▁at ▁low ▁temper atures ▁due ▁to ▁the ▁slow ▁flow ▁through ▁the ▁fuel ▁filter . ▁ ▁Engine ▁performance ▁B iod ies el ▁has ▁higher ▁bra ke - specific ▁fuel ▁consumption ▁compared ▁to ▁dies el , ▁which ▁means ▁more ▁b iod ies el ▁fuel ▁consumption ▁is ▁required ▁for ▁the ▁same ▁tor que . ▁However , ▁B 2 0 ▁b iod ies el ▁bl end ▁has ▁been ▁found ▁to ▁provide ▁maximum ▁increase ▁in ▁thermal ▁efficiency , ▁lowest ▁bra ke - specific ▁energy ▁consumption , ▁and ▁lower ▁harm ful ▁em issions . ▁The