Goal is to average 5l per 100km in all driving conditions. Generally I can match my highway and city driving fuel consumption so this shouldn't be hard as an average. Update for anyone who wants to know this car ended up averaging 5l/100km easily.
y1 gearbox, 3200rpm at 100km/h original s1/j1 3500rpm at 100km/h
175/65r15 llr tyres
Mini 15x5.5 12lbs alloys
aero replacement trunk made for glass over plywood.
Smooth wheel covers