No personal experience, but this is what's stated on Costco's travel site:
It sounds like the additional driver and stated required info is added onto the reservation record.For Alamo and Enterprise, the additional driver fee is waived for rental in the U.S., Canada, UK, France, Germany, Ireland and Spain. For Avis and Budget, the fee is waived for rentals in the U.S.
The additional driver must meet all renter requirements, appear at the rental counter with the primary renter, present a valid driver's license and present a major credit card in their name at the time of rental (they do not need a valid membership card). Additional fees will apply for drivers under 25 years old.
Please note, some rental car locations may allow your spouse as a secondary driver, plus your Costco Travel additional driver. This means you can have up to three drivers included in the cost of your rental. For details, contact the rental location.
I always do this also. Just wanted to add that you can get your Costco membership card on your phone on the Costco app. While I am not a big fan of apps in general, this one is helpful even though the picture is 20 years old!I always do Alamo/Costco. Costco only asks for the name of the principal driver. However, when I complete the online checkin on the Alamo site, I can add the name/address/driver’s license for the second driver. I am usually asked for the DL of the second driver (along with my DL and credit card) at the exit booth in the garage. I always do skip the counter and go directly to the garage when available (as it is at MCO). Since I also login to Alamo with my Alamo Insider number, the checkin pre-populates my DL and CC information, so all I have to enter is the second driver information.
When we rented with Alamo/Costco at San Diego, skip the counter was not available, but I had completed the checkin in advance as usual. There, I used a kiosk to avoid going to the counter. Had to scan both DLs along with the credit card to complete the kiosk checkin.
One other thing. Costco indicates that you need to show your Costco membership card when picking up the rental car. I have never been asked for this at MCO, and for many years I did not carry my Costco card with me. Then I was asked for it at TPA. Fortunately, my DW had her Costco card in her wallet the first time this happened, and she was on the rental as a named second driver from the online checkin, so I didn’t have a problem. The next time this happened, again at TPA with the same gate agent, I had my card ready, and now always carry my Costco card when renting a car, just in case.
Just saw this as I was checking out at Costco this morning. I usually use the self-scan check out, so had not realized I could do this. I’m all for eliminating one more card from my wallet.I always do this also. Just wanted to add that you can get your Costco membership card on your phone on the Costco app. While I am not a big fan of apps in general, this one is helpful even though the picture is 20 years old!