Car rental, decoded
Upgrade
Also known as: vehicle upgrade
Receiving a higher class of car than booked. It can be complimentary (offered at no charge, often when the booked class is unavailable) or paid (accepted at the counter for a fee).
What you may think
An upgrade is always a free perk.
What is actually happening
An upgrade is sometimes complimentary, but at the counter it is often a paid offer; you can decline it and keep the class you booked.