Yup, this is a domestic rental, driving in NM, CO and UT. Only reason I would use the Amex Plat is to get benefits of 4 hour extended rental and possibility for upgrade. From what I understand, as I don't have any primary insurance (I don't own a car) the secondary offered by Amex would kick in as primary should anything happen. That said, I always prefer to use my Chase cards for rentals since I get more points and they have primary insurance.

You really should not count on an upgrade. In HLEs, even PC members don't usually get upgrades beyond Full Size.

Especially not on a one-way.

The Amex Plat grace period works very well, but I learned the hard way a few weeks ago that the 29 minute grace period for late returns doesn't apply when you get the 4 hours from Amex. I ran into a traffic madness getting into DCA (which I've never encountered before) and the vehicle was scanned 4 minutes after the scheduled return time and generated an extra charge. When I inquired, the manager confirmed that because I had the 4 hours from Amex, the system would not apply the 29 minutes late arrival grace.

One more question:

If I book through priceline using autoslash -- after ticking the box for Amex platinum -- can I use a chase card to pay and retain the discount I got from listing my Amex plat? If I wasn't already looking into all of this I wouldn't even necessarily know that the Amex plat checkbox got me a lower rate on priceline. There's nothing to indicate that on priceline, though if you look up the reservation # on Hertz it shows the Amex code. I don't want to show up and be forced to use my Platinum to get the rate. Would prefer to put it all on a chase card with primary insurance. I've given up worrying about an upgrade on the routing I have since it seems unlikely, and in any case I'm fine with a mid-sized car.

Yes, you can pay with any card you like. The requirement is to be an Amex Platinum cardholder to use the Amex Platinum CDP (discount code).

Checking the AutoSlash box for Platinum does not mean the reservation is necessarily using that CDP though.

So even if it is definitely using the Amex CDP code and giving me 4 free hours free I can pay with my Chase Sapphire Preferred, for instance? I could have sworn when booking through the Hertz site it said you had to use the platinum for the booking. Of course when going through Autoslash/Priceline one wouldn't have any idea what codes or requirements are in play unless they load the confirmation number on the Hertz website.

If you have a question about what CDP is used in one of our offers, just email [email protected] and we'll be happy to tell you.

I wanted to share something useful about the 4 hrs free benefit with this CDP. Those 4 hrs are added on the basis of your ACTUAL pick up time. Just take a look at your printed or emailed contract & you can calculate precisely by what time you have to drop off the car. I can also confirm that one does NOT get the 29 min late return grace period when using this CDP.

What I would like to know & @AutoSlash / any body can chip in here is what if I book only for 24 hrs or 26 hrs using this CDP but return it at say, 27 or 28 hrs from the actual pick up time, will I still only be charged for 24 hrs?

Yes, it works the same way with the non-Amex Plat CDP. For example, if you have a reservation for a pickup on 8/1 at 10AM and a return on 8/3 at 10AM, but arrive an hour early and actually pick up at 9AM on 8/1, then the rental would be due back by 9AM (not including the 29 minute grace period) or you would be charged for an extra hour, even though your reserved return time was for 10AM. Rentals are always based on a 24-hour day.

As for your other question, we would assume that the 4-hour grace period would apply based on your actual rental times regardless of what you reserved. Using the example above, if you had the Amex Plat CDP on your reservation and booked for a pickup on 8/1 at 10AM and a return on 8/3 at 10AM, you could return up to 2PM on 8/3 without a penalty. Likewise, you could have reserved for for a pickup on 8/1 at 10AM and a return on 8/3 at 2PM originally, but you would not then be able to return at say 6PM the same price. You've already "used" the 4 hours, so they wouldn't apply again. In short, rentals are based on a 24-hour day and the 4-hour grace period is based on that.

To take advantage of the amex platinum grace period do I put my return time 28 hours after my pickup time or do I just put my return time 24 hours after pickup and then return it no later than 4 hours past that time? I'm worried that amex has a disclaimer that says it may not be available at all locations

I would set it for 28 hours after. Then you know exactly what you’ll be charged. No penalty for returning earlier.

As far as I know, it's the latter.

Thanks to all those that posted. I don't currently own a car, but I kept my insurance with no car assigned as that will likely save me money when I buy a car. So going forward I'm paying with my CSP and using the Amex Platinum CDP for my reservations. Not only does it give you a bigger discount than AAA, but you get the 4 hour grace period which you don't with AAA.

One observation, is that if you go over by more than a minute, you won't pay an additional day charge. The sales tax will remain the same. However, the fees associated with your rental will be higher as that's another day. I know because I booked a prepaid a couple of weeks ago, and ended up paying almost $5 more than estimated, and in my past experience on non prepaid bookings, the "estimate" was correct down to the penny. Just something to think about if you were only going to use a few minutes of the grace period.