v ro let ▁Mal ib u ▁Hy brid . ▁It ▁oper ates ▁similarly ▁to ▁other ▁m ild ▁hy br ids ▁with ▁a ▁start - stop ▁system , ▁in ▁that ▁it ▁sh uts ▁down ▁the ▁engine ▁as ▁the ▁vehicle ▁comes ▁to ▁a ▁stop ▁and ▁instantly ▁rest arts ▁it ▁when ▁the ▁bra ke ▁ped al ▁is ▁released . ▁ ▁The ▁B AS ▁system ▁is ▁capable ▁of ▁providing ▁mod est ▁levels ▁of ▁power ▁assist ▁during ▁launch / ac cel er ation ▁and ▁similarly ▁mod est ▁levels ▁of ▁" bl ended " ▁reg ener ative ▁bra king ▁during ▁dec eler ation . ▁Although ▁unable ▁to ▁operate ▁in ▁pure ▁all - elect ric ▁E V ▁mode , ▁the ▁B AS ▁system ▁provides ▁improvements ▁to ▁both ▁city ▁and ▁highway ▁fuel ▁efficiency ▁over ▁similar ▁non - hy brid ▁ ▁versions . ▁ ▁In ▁more ▁powerful ▁e Ass ist ▁versions , ▁a ▁B AS ▁system ▁can ▁add ▁power ▁to ▁prevent ▁excess ive ▁g ear ▁changes ▁under ▁variable ▁load . ▁According ▁to ▁the ▁E PA ▁the ▁ 2 0 0 9 ▁Sat urn ▁Vue ▁B AS ▁hy brid ▁g arn ers ▁an ▁improvement ▁of ▁ 3 2 % ▁city ▁( 1 9 > 2 5 mp g ) ▁and ▁ 2 4 % ▁highway ▁( 2 6 > 3 2 mp g ) ▁making ▁the ▁combined ▁economy ▁improvement ▁ 2 7 % ▁( 2 2 > 2 8 mp g ) ▁over ▁the ▁base ▁ 4 cy l ▁F WD ▁version . ▁The ▁system ▁is ▁reason ably ▁simple ▁and ▁in exp ensive