Engines are getting more efficient with every passing year.
What you often find is that the slightly smaller engine is not optimum for the vehicle but the larger engine is.
I drove two Ford Cortinas, back in the day, and the 1.6L gave far better mpg than the 1.3L. Both engines were the same except displacement and both were from the same model year.
2006 Honda Jazz 1.2i-DSi S Vivid Blue Pearl
I'd agree with above. And increasingly tighter emissions regs forcing car makers to eek every tenth of an MPG out thier car. Some of the new VW group cars put the car in neutral and turn off the engine entirely on long hill descents.
I've often found smaller underpowered cars can be less efficient as you have to work them so much harder, some of the hills here I've been flat to the floor and knock it down two, sometimes three gears just to get up. In my more powerful cars, I'm in 6th, barely touching the throttle at all, just a nice lump of torque as the turbo spools and pulls you up.
I'm not ready for the "toaster" path of advancement (driving). In Naval Air - during the "Greatest Gen" days -- - - propellor aircraft to jet aircraft transition - the expression "Take it slow and easy if you want to get along with me" became the sane approach to the appropriate learning curve.........jets ate a lot of fuel, jets did not accelerate like prop aircraft............
You had to plan ahead - especially with a carrier landing...........
That's where I am - - - - planning ahead.
My 1.4L Jette is REALLY fuel efficient. And reliable. And fun to drive.
I know fossil fuel ain't forever. I know we have choices,.
Well, if Edmunds is to be believed, moving to a new Jetta would bump mpg city/hwy 1 and 2mpg respectively with 1 mpg increase in combined mpg. And a smaller fuel tank means slightly more often visiting the pumps.