Simply sprinkle on enough to cover the stain (Image 1), and then grind it into the stain with your foot (or a brick, if you prefer not to run the risk of getting oil on your shoe) to break it up and increase the absorbency (Image 2). Use a stiff broom or brush to sweep up the powder.
Having removed the surface oil, you're now ready to clean up the soaked-in residue. For this part of the job, you'll need a stain remover (there are a number of commercial concrete cleaners available) and a stiff-bristled brush. Simply spray on the cleaner, use the brush to work it into the concrete.
Before starting the pressure washer, be sure to attach the garden hose and turn it on -- this will keep the pump cool so it won't burn out. Cover any nearby plants with a tarp before beginning -- the cleaning products can be harmful to plant life, and the powerful pressure washer is capable of washing plants right out of the ground! Turn on the pressure washer and point it at the spot to be cleaned. In just a matter of seconds the residue should be removed (be aware, however, that a stain that has been in place for a long time may never be completely removed). If the concrete has any other stains such as algae, mold or mildew, use the pressure washer to remove these at the same time.
After cleaning the concrete, sprinkle a few drops of water on the surface. If they soak in within five seconds, go ahead and seal the concrete. Use any of a number of products on the market that are suitable for sealing concrete -- check at a local home-improvement center for recommendations. Apply the sealer with a brush or a roller for an attractive, lower-maintenance finish.