i drive a Hyundai accent 1.5 Petrol which returns me 12-14 kmpl on an average driving while my VW Jetta 1.8 Turbocharged returns 11-13kmpl. Engine cc does count but to some extent when you compare a 1litre to 3 or 4 litre engine. its an engineering difference that makes them fuel efficient
Another simple example which shows " Engine Size (in CC) Alone doesn't Matter the fuel consumption/economy "
Difference of fuel economy in same Engines - (the only difference in both engines is the Fi & oil cooler)
avg of karizma R 223cc (carb version) - 38km/l
avg of karizma zmr 223cc (Fi verison) - 45 km/l (despite being 10 kgs heavier than the above one)
me on my rtr 160- 30 best
dad on his p200- 45.
that tells a lot.
factors are there, but we just cannot expect a mitsu 3000gt to give the same mileage as lambo murcielago.
still,engine tuning matters. a bmw m5's 5 litre v10 is more efficient than a vipers 8.7 litre v10.
My one cent ,fe depends upon the efficiency of engine & how you utilise it
e.g. 2 stroke engine has less efficiency than 4 stroke same capacity engine this answers why RX 100 has less fe compared to ct 100
& the power to weigh ratio is also important e.g.swift & dzire has same engine & front facia(same wind registance) but dzire has less power to weigh ratio because of 40kg extra weight so have less fe than swift
i would vote for may or may not. it depends on the car actually.
i would compare the innova D-4D & scorpio mHawk - the scorpio is heavier, has 20 bhp more & is geared for performance, compared to the innova. everything suggests the FE of innova should be higher but its the other way round.
maybe the reason is scorpio's engine is 2.2 & innova's engine is 2.5, but i dont think thats the actual reason. i feel, since the scorpio has more torque, it needs only a light tap on the throttle to get it moving in the city. so overall, it runs at a much lesser rpm throughout compared to the innova. so it turns out to be more fuel efficient.
of course, but engine size would matter if we compare a 1.2 petrol to a 3.0 V6 petrol!