From
https://www.hertz.com/rentacar/ememb...umGoldbenefits
For 5*:
Upgrades and Coupon Offers
Subject to vehicle availability, one-car-class upgrade is offered at participating Hertz locations the U.S., Canada and participating European locations with a 2-hour advance reservation. Maximum upgrade is to a Premium car with a minimum reserved Mid-Size vehicle. For Compact 4-Door rentals, maximum upgrade will be to a Full-Size 4-Door car. Guaranteed upgrade is to the next car class only. This excludes Special Equipment such as Minivans, SUVs, Hertz Adrenaline CollectionŽ, Hertz Green Traveler Collection and Hertz Prestige Collection vehicles.
For PC:
Guaranteed Upgrades, Availability and Coupons
Guaranteed one-car-class upgrade or comparable benefits are offered at participating Hertz locations in the U.S., Canada and participating European locations. Maximum upgrade is to a Premium Car with a minimum reserved Mid-Size vehicle. For Compact 4-Door rentals, maximum upgrade will be to a Full-Size 4-Door car. Guaranteed upgrade is to the next car class only. This excludes Special Equipment such as Minivans, SUVs, Hertz Adrenaline CollectionŽ, Hertz Green Traveler Collection and Hertz Prestige Collection vehicles