In simple terms, yes. Take your car back clean and you won't be charged. It's tricky to guess when a rental company might decide a car is too dirty. If a car smells of smoke when it's returned, the rental company will charge a cleaning fee, even if the car is otherwise clean.
How clean do you have to return a rental car?
You don't need to wash it. The rental company will wash the exterior no matter how dirty it is. As long as the grime can come out in a car wash, you're fine no matter how dirty it is. Scratches or tar or other exterior blemishes are another matter.
Does enterprise charge you if the car is dirty?
Does Enterprise charge a cleaning fee? No; however, we expect rental cars to be returned in the same clean condition that they were first rented in. If a vehicle requires excessive cleaning or special cleaning products, a cleaning fee will be applied to your overall rental cost.