Removing oil stains from concrete is beating me

Old oil on concrete: put down a thick paste of baking soda or powdered laundry detergent with a bit of water, leave it to dry, scrub with a stiff brush and rinse. Repeat if needed. Worst ones you can use a poultice of cat litter soaked in a solvent like mineral spirits, covered and left overnight to draw the oil out. Gloves and ventilation for that one.