Rental prices on the website are exclusive of fuel costs. You must therefore return the vehicle with the same amount of fuel as it had at the start of the rental.
If the fuel level is inferior at the end of the rental, owners can make an adjustment to be compensated for the difference.
If the fuel level is superior at the end of the rental, you can proceed to make an adjustment yourself, if the owner didn't take care of it for you.
NB: For Getaround Connect rentals, a £15 penalty will be applied if you give the car back with less fuel than at the start (if the difference is 15% or more).