PaPaDan almost won what was behind door number three.
Here's a little trick. Oil stains in natural stone or tile grout or concrete generally get there and penetrate over time, so to get the stains out you would also use time.
The trick is a poltice. To make a poltice for this stain removal mix some kitty litter with mineral spirits in a bucket. The kitty litter will soak up a bunch of spirits. Once the kitty litter is saturated with the mineral spirits and won't take no more liquid, add some more liquid. Pour the mixture on the stain and let it sit for a few hours, maybe even over night if it isn't too warm outside when you do it. After a few hours hose it off thoroughly. The mineral spirits residue may take a few days to disapate, it just depends on how porous the concrete is to begin with.
The poltice will naturally draw the oil out on its own, trying to scrub the stain only further imbeds to oil into the microscopic pores of the concrete and worsens the situation.
More than one application may be necessary, if so then let the area dry and rest for a few days before going at it again. During this time some of whatever remains will naturally try to rise with the evaporation process of the mineral spirits that has migrated deep into the concrete.