Grease is tough to take out of fabric. Soap and water alone just won't cut it, you need something to break up the grease.
Here's what I have done in the past.
Use Goop or GoJo hand cleaner this is specially made to cut down grease when cleaning your hands. Then with a damp cloth with just water rub away the Goop or GoJo cleaner that you used. Then as a final clean use the "Prestone Interior Cleaner", thats the stuff that they sell everywhere from autozone to walmart.
Just to be on the safe side before you do this test the steps above on a small section (that can't be easily seen) that has the same material that the grease is on.
Good luck.