In Portal 2, which gel makes surfaces slippery and increases speed?

In Portal 2, which gel makes surfaces slippery and increases speed? Propulsion Gel makes surfaces slippery and increases the player’s speed.

Propulsion Gel is the orange gel in Portal 2. When it coats a surface, characters can move across it more quickly, allowing players to build momentum and reach otherwise inaccessible areas. Puzzles often require directing the gel through pipes, portals or falling streams so that the correct route becomes a fast-running path.

The gel belongs to a trio of paint-like substances introduced in Portal 2. Blue Repulsion Gel makes players and objects bounce, while white Conversion Gel allows portals to be placed on surfaces that normally cannot accept them. Water can wash away gels and return a surface to its normal state.

The movement gels originated in Tag: The Power of Paint, an independent game whose creators later worked with Valve. Propulsion Gel is easy to confuse with Repulsion Gel because both alter movement, but their effects differ: propulsion enables faster running, whereas repulsion produces jumps and bounces.