For many simple cleaning jobs, you don’t need detergent; the water blasting out of your pressure washer is enough to get the job done. But for many tasks, particularly those involving dried or tough grunge, you’ll get the best results by using a detergent.  Some pressure washers have built-in tanks for detergent, while others require you to set a tube into the bottle of detergent so the pressure washer can suck it directly from the bottle. Either way, your best option by far is using a detergent specifically formulated for pressure washers. These detergents cut through grease and grunge yet don’t get soapy or foamy, leave a film on whatever you’re cleaning, or make the ground slippery. There are formulas for a variety of purposes: cleaning cars, siding, wooden decks, concrete, and driveways to name the most common. There are also many general-purpose pressure washer detergents, which are a good choice if you expect to use your pressure washer for a variety of cleaning jobs around your property.  While some people use dishwashing detergent, this isn’t recommended, as there’s a good chance you’ll end up with an overflow of suds. And pouring dishwashing detergent into your pressure washer’s tank could destroy or damage the machine.