At the beginning of combat on your turn, return target Vehicle card from your graveyard to the battlefield. It gains haste. Return it to its owner's hand at the beginning of your next end step.
Greasefang is a reanimator-tempo commander built around cheating expensive Vehicles out of the graveyard. You self-mill or discard a giant Vehicle, then attack with Greasefang to reanimate it with haste and crew it for a lethal swing or a brutal attack trigger before it bounces back to hand at end step. The deck wins fast by stacking enormous Vehicles and protecting your combat step.
Cheats out huge Vehicles for free every combat, generating massive mana/tempo advantage
Can win as early as turn 3-4 with the right enablers in hand
Self-bounce protects Vehicles from sorcery-speed removal and resets ETB-less value
Black-white access to top-tier reanimation, tutors, and protection
Extremely commander-dependent; without Greasefang the deck stalls
Vulnerable to graveyard hate which shuts off the whole engine
Needs both a Vehicle in the yard and a way to crew/attack, so it can clunk
Vehicles must survive removal during your combat to do anything