This may or may not help you. But I use a de-greaser that was made for cleaning mildew from aluminum but does wonders with grease and oil. (Go Figure)
Only catch is that on asphalt I have had it eat the tar out of the pavement if put on too strong.
This stuff is bio-degradable and smells nice too. Work's fairly well on just about anything from carpet to engine's. Even remove's some rust stains.
It is called "Frank's Special Cleaner" I get it from an auto detail supplier. It is made by Pro and Buford's.
If interested I can give you the local dealer info and he could probably tell you where to find it in your area.
------------------
Ronniels
AHR Tidewater, Inc.
Va Beach, VA 23456
(757) 368-5495