Rental at LAS for trip to Zion and Bryce Canyon National Parks. Car was OK. It snowed on the way back to LAS and, of course, there was some salt and road grime on the car -- nothing unusual for winter driving (actually fairly mild). When I went to return the car I was told they would assess a $25 cleaning charge because they would have to do additional/exceptional work to clean it -- but then suggested I go to the car wash down the street, which I did. I chose the cheapest quick wash and the car was spotless afterward (and that would have been the equivalent of Hertz's wash, at the very least). Another Hertz scam.
As stated in the Terms and Conditions, if the vehicle requires more than Hertz's standard cleaning on its return, Hertz may charge the customer for the actual costs incurred to have the vehicle cleaned. This required nothing more than a simple car wash which is done on all returns. If Hertz's logic carried forward from LAS, then they'd tack this on for every vehicle rented anywhere where it rains or snows. This is normal, not unusual and not excessive.
ADDED: From reading other reviews I'm shocked that the Nevada Attorney General has not taken action against them.