Yes your correct, on a different not the new ecoboost ford motor should be getting good good MPG. the 4runner would do good with a diesel motor, toyota just didnt pick the right one, theres does 25 Imperial MPG which is like 21mpg US.
The closest Ford competitor to the 4runner is the unibody Explorer. And the 2011 Explorer AWD gets 17/23/19 combined EPA. This is with their 3.5L V6 (smaller engine) with 6-speed auto (again, advantage over 4runner). Yet, it still about the same as the 5th gen 4runner. Curb weight is about the same. YET, despite all this going for the Explorer, the 5th gen 4runner achieves the same fuel economy!
Now, if you want to talk about Ecoboost, then you have to go to the Ford Flex. Here, again, the EPA ratings for the Flex with 3.5L V6 is 16/22 (AWD). With the Ecoboost engine, you're at 16/21 (AWD). Flex curb weight is about 200 or so lbs more than 4runner.
Remember, Ecoboost was made to achieve V8 power with V6 efficiency. It was NOT advertised as V8 power with 4-cyl efficiency! And, power is really not a big issue with the 5th gen 4runner since it can hang in acceleration with Flex and Explorer, with or without Ecoboost.
As for the Toyota diesel used in the Prado overseas, this is what i found:
"the turbo-diesel engine lists a fuel consumption figure of 8.5 l/100km in automatic guise, and 8.8 l/100km when paired with the manual transmission."
Not sure how those numbers add up to EPA ratings....
EDIT: from brief googling, 8.5 L/100km is equal to about 33 mpg. That is not half bad!!
