My 2014 Mazda 3 2.0L 6MT hatchback will dip to around 6.5 L/100KM if I drive it gently to and from the cottage (average speed ~80 km/h, very light traffic), but my commute average has it burning almost 2L more per 100 km. Part of the reason is I swapped on 18" wheels and summer tires and have also done a few bolt-on…