Fuel discrepancy by Avis staff

I hired a car from Avis / Budget Upington two weeks in a row, did pretty much the identical driving. First week's fuel for a Merc C200 was 32 litres for 497 km. Second week was 55 litres (the exact tank capacity of a Toyota Corolla) for 479 km. Does a Corolla only do 479 km on a full tank? I get the mindless response “fuel consumption differs from vehicle to vehicle hence the discrepancy in the refueling.” 36% difference. Prior to this, and in the absence of any response for 8 days, I was asked to rate Avis Customer Care service.