[aerohead]

1) I left my workbook at home, but I believe that for the New European Driving Cycle, a 10% change in weight equates to approximately 1.5% change in fuel economy.
2) In the USA, EPA fuel economy testing is done with 300-pounds ( 136-kg ) added to the vehicle.
3) The Auris is reported with a curb weight from 1190-kg, to 1480-kg.
4) So a 10% weight reduction would be 119-kg, to 148-kg, to see a 1.5% difference.
5) Or 79.33-kg, to 98.66-kg to see a 1% change.