As always, it really depends on a few certain factors, and in this case, it’s mostly the surfaces that you’re about to clean and the types of dirt you have to deal with. For cleaning cars, yes, you should use some sort of detergent product to get rid of all the dirt and greases on them. Not to mention that some car cleaning products even make your car shinier while giving it a protective layer. But for cleaning concrete driveways or sidewalks, your detergent will not be as important as the coating products that you’re using. Sure, they could make it relatively easier to deal with greases and the likes. But these stains can always be spot treated, which would be a lot more effective. Not to mention that you can easily spill some of the detergents onto the lawn and potentially kill the grasses. The only thing that makes detergent useful is that they loosen the dirt on your concrete to make it easier to clean. But you can also achieve great results with simply high-pressure spray from your machine. On the other hand, with good coating, you can prevent dirt from getting on the concrete surfaces and save yourself from most cleaning tasks anytime soon.