We have used a lot of concrete cleaners on this show, even recently compared water based to solvent based cleaners and found them rather equivalent.
Here is a new one that is rather amazing. It is called Oil Lift. The difference with this one is that it is totally ecologically friendly, no harsh chemicals. It does not dissolve the oil into a suspension but foams it up to the surface and then breakes down the carbon chaines to make it bio-degradable.
Different from all other cleaners, you have to be more patient as it does its work slowly, but once ready, you can just rinse the oil away. As with all concrete cleaners, it works best with a power washer but a hard garden hose spray is amazingly effective. In Canada it is available at Canadian Tire, but the store managers hide it with all the solvents. We need to beat up on the shelf stockers to give this ecological solution that actually works a bit more prominence in the stores.
Click here for more on Oil Lift.