That seems to be a normal event, i've got a FIAT Brava 1.2 82hp and the books say it'll do about 6/6.5l per 100kms, i'm doing about 8/8.5... and i use it on highway most of the times and run at about 100kms/h at 2900/3000rpm... so they seem very optimistic about things when i read the brochures!