Back in 2010 both me and my parents owned Mazda 3 (model year 2009) cars. They live in the suburbs with no traffic lights for a kilometre in every direction. I

Back in 2010 both me and my parents owned Mazda 3 (model year 2009) cars. They live in the suburbs with no traffic lights for a kilometre in every direction. I lived in an inner city (CBD fringe) apartment. Their car consistently reported 7.1 L/100km average whereas mine consistently reported 12.5 L/100km average. Both would get the same ~6.5 on highway driving. Point is, road conditions and driving style affect fuel economy far more than the marginal difference between vehicles of a similar size class.