Ok, so I changed my differential fluid. First time I've ever done that, so GO ME!! Anyway, I spilled a little on the cement of my carport, and I'm sure you all know that stuff stinks like crazy. I did find a way to remove it though. Clean as much of it up as you can with shop towels, paper towels, whatever. Get some trisodiumphosphate (tsp) powder. I had some on hand from Lowe's from when I put down my linoleum tile. Anyway, wet the cement a bit and sprinkle the tsp powder over the spill. Scrub on it for a bit with a stiff bristled brush and let it sit for a bit. Mine sat for about fifteen minutes. Then wash it off with a hose. There's still a little bit of a stain on the concrete, but it's 90% gone. I'm sure there are other ways to remove it, but that worked really well for me.