The Oil Slide is one of Hakan's special attacks in Street Fighter IV.
Input
+ 
(followup with /
)
Description
Executed by performing a quarter-circle forward motion and pressing punch, Hakan dives at the ground and slides on his belly toward the opponent to knock them over. If successful, the player can press punch one more time to continue sliding past the opponent, stand up, turn around and bodyslam them while they're on the ground. Alternatively, the player can press kick to end up with an Oil Shower.
How far he slides and how much damage the initial knockdown does is determined by the punch button pressed first; light punch does the least damage and slides the least distance, heavy punch does the most damage and slides the most distance, and medium punch is somewhere in between. There is also an EX Special version which slides about as far as the light punch version, but does 10 more damage than the heavy punch version.