In the 70s had a twin cam Escort which with the best will in the world delivered 25mpg and when "driven hard" 10mpg and when comepted about 7
Now have an RX-8 which with the best will in the world delivers 25mpg and when "driven hard" 18mpg and when competed about 18mpg. So I call that improvement
Rotary the worst example perhaps
But the difference in fuel consumption for equal performance is huge in piston engines due to better fuellling, air/fule mix and spark as well as advanced timing.
But, I came to comment mroe on the relative merits of the weight gain.
Yes, I hate the weight gain for waht it does to performance and fuel consumption.
BUT the advantage for the vast majority it brings in less death and serious injury is a reaonable balance in the equation. ( Just wish when they did "Performance" versions they'd let us make that risk choice and get somethgin REALLY light )