Haven't been all through the thread to see if this is covered (so apologies if this is repeating earlier experience) - Hertz has major issues with one ways to the airport - whether using On Demand / 24/7 or regular Hertz.

In the the case of the former, they will leave you hanging right as your reservation was due to start with "car not available" message. You can wait for 40 mins trying to get an agent, or you can try to find a cab, because Hertz is doing nothing for you at this point. After this happened to me twice, I gave up trying to use HOD for one ways to EWR from Manhattan. After lots of exchanges I finally got to a regional VP who explained that their Ts and Cs don't guarantee any car availability - in contrast to standard rental car reservation in NY state.

I have used regular Hertz one way rentals t EWR in the past when they are trying to reposition cars. Availabaility has been much less than normal in the past year and there is ALWAYS a problem at EWR when returning the car as in every case (I have done it 5 or 6 times) they will try and charge you a regular daily one way rate - often north of $200 no matter what the reservation said or you were quoted. I have also paid the $25 one way rate, only to be charged taxes on a normal daily rate - it's a mess and requires you to deal with confused counter staff rather than the rapid return crew.

Buyer beware - for me the hassle outweighs the savings after numerous bad experiences.