Is it possible to 5 feet in a grease spell floor?

[勝20100]

Is it possible to 5 feet in the area affected by grease?

The rules indicate that it is not possible to 5 feet in difficult terrain but the spell doesn’t indicate it creates difficult terrain. At the same time the rules for difficult terrain are to move at half-speed and if the terrain is slippery it forces acrobatics checks as the spell does.

I would think that using 5 feet in grease is not possible.

[Snowleopard]

I would rule that a 5foot step in a grease spell is out of the questions as it would cost double movement and therefor would be a move action and no 5 foot step. And that could mean an attack of opportunaty and no full round action following it.