When I blow a hose on my tractor, I use my pressure washer and pressure washer degreaser from walmart. I use spray it on everything with the pressure washer, let it set for a few minutes then hose it off. But then, I am not too fussy about having a spit and polish tractor. I work it in dirt and dust and dont worry too much about a little dirt on it. But the pressure washer does a good job. Cat litter is cheaper than oilsorb material is does a good job on concrete. Simple green might work on the concrete after the cat litter has soaked it up a bit. I dont think you will ever get the stain out completely though due to the porous nature of the concrete. Just scrub it good and then keep some cat litter on it for a few weeks and it will continue to wick out anything that is left. Oil leaks in the garage is a good reason to put down an epoxy coating (before the oil is spilt)