The changeover to the Hertz computer systems may have something to do with it,there are many problems with prepaid vouchers. I know that in the old system you were not allowed to earn Express credits on a prepaid voucher (the way it was setup)& I'm sure that has not changed with the new system since its even more restrictive. IMO, if the fuel is included in the voucher, the manager could have put a note on your contract to bring it back empty and tried to correct it later.