You can use something simple like Dawn dish soap for various degreasers that you can find at Lowes or Home Depot. Zep Purple works well in particular.
Our favorite product, Simple Green Oxy Solve Total Outdoor Cleaner, was specifically formulated for use with a soap siphon for pressure washing.
It also included instructions on how to mix it for use in a spray bottle. In our side-by-side comparison, Simple Green cleaned as well or better than the others in the same amount of time.The product is safe for use on a wide range of surfaces and was the only product we tested that is also Safer Choice certified by the EPA. A good pressure washer for concrete should have a nominal pressure of approximately 3,000 pounds per square inch and a flow rate of at least 2 gallons per minute. To use it, apply the product dry or wet to the stain with a broom and leave it on the surface; no need to sweep or wash it.
