Z63R said:
It's no joke, actually; big inches at very low RPM yields excellent fuel mileage. Pete Brock told me that. Yeah, THAT Pete Brock.

But just try to keep your foot out of it... LOL. Impossible.
the reason pushrods get good mileage is that thier displacement allows for a lower torque peak, they also have less friction than OHC.
Larger displacemnt = less econoy Because the engine doesn't work as hard, and wastes gas idleing, and accelerating.
one of the largest inhibitors to efficentcy is the throttle. Engines work best at WOT, less restriction, a engine needs to work as close to 100% as possible but rarely is working near 60%.
technolgyies like the CVT+electronic throttle, uses the CVT to keep the engine working harder and longer, squeezing as much MPG out of every drop of gas.
using light throttle on a big engine, is worse than using heavy throttle on a smaller engine.
The 1.8 vs 2.3 would be
22/32 2.3
27/37 2.0
30/40 1.8
I am sure some people enjoy drivng a focus 2.3 with worse economy than the Camry. most won't and some will apreciate the added MPG over 11hp and 11 ft/lbs of torque.
honestly the 2.3 doesn't make enough extra hp to make up for the 25%-36% loss in economy.