▁vis cos ity ▁and ▁clean lin ess ▁is ▁a ▁factor . ▁Use ▁of ▁the ▁incorrect ▁oil ▁type , ▁i . e . ▁S AE ▁ 1 0 W 4 0 ▁instead ▁of ▁S AE ▁ 5 W 3 0 , ▁or ▁the ▁failure ▁to ▁change ▁the ▁engine ▁oil ▁or ▁oil ▁filter ▁at ▁factory ▁recommended ▁intervals , ▁can ▁also ▁significantly ▁imp air ▁system ▁performance . ▁ ▁In ▁ 2 0 0 1 , ▁G M ▁show c ased ▁the ▁ 2 0 0 2 ▁Cad illa c ▁C ien ▁concept ▁car , ▁which ▁featured ▁North star ▁XV 1 2 ▁engine ▁with ▁Dis p lacement ▁on ▁Dem and . ▁Later ▁that ▁year , ▁G M ▁deb uted ▁Op el ▁Sign um ² ▁concept ▁car ▁in ▁Frankfurt ▁Auto ▁Show , ▁which ▁uses ▁the ▁global ▁XV 8 ▁engine ▁with ▁disp lacement ▁on ▁demand . ▁In ▁ 2 0 0 3 , ▁G M ▁un ve iled ▁the ▁Cad illa c ▁Six teen ▁concept ▁car ▁at ▁the ▁Detroit ▁Opera ▁House , ▁which ▁featured ▁an ▁XV 1 6 ▁concept ▁engine ▁that ▁can ▁switch ▁between ▁ 4 , ▁ 8 , ▁and ▁ 1 6 ▁cyl ind ers . ▁ ▁On ▁April ▁ 8 , ▁ 2 0 0 3 , ▁General ▁Mot ors ▁announced ▁this ▁technology ▁( now ▁called ▁Active ▁F uel ▁Management ) ▁to ▁be ▁commer cially ▁available ▁on ▁ 2 0 0 5 ▁G MC ▁En voy ▁X L , ▁En voy ▁X U V ▁and ▁Che v ro let ▁Tra il B la zer ▁EX T