In my experience,no matter what you use,you only get some of the oil or grease off--the rest sinks into the asphalt or cement and stays there for a long time...be careful with a pressure washer--I know on asphalt they can cut right down to gravel REAL fast!..
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Eventually years of rain,sun,and wind will erase all traces of it though--the spot where my '72 K5 left gear oil deposits where I parked it back in the 80's was a thorn in my dads side,so I rented a pressure washer and got some "TSP" (Tri-sodium-phosphate) from a paint store and scrubbed the area good and when I blasted it with the pressure washer,it removed some of the top layer of asphalt...
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I failed to get much of the stains out,and decided to just let things lie..now,some 25 years later,you cant detect any sign of stain at all...not sure if the oil sinks all the way through the asphalt,or simply gets washed away over time..
I never had much luck using "Gunk" or oven cleaner on tar or concrete,and most of the other stuff I tried like Greased Lightning or Simple Green,Castrol Super Clean,did remove some of it,but not all..
They used to sell some kind of powdered bacteria stuff to clean oil off concrete years ago--we used it in trade school,all it took was a small amount sprinkled over the stain,you wet it a little and let it sit a day or two,then washed it off,and it did do a remarkable job--supposedly the bacteria eats the oil ...cant recall the name of it now..
