Experience from my friends with the 4-cyl. engines in their Jeeps is that the reduced power output winds up being compensated by lower fuel economy. They compared their fuel usage compared to that of a 6-cyl. (mine) and found that they were actually getting worse mileage than the larger engine since they were having to push harder on the narrow pedal more often to do their normal driving.

This is based on a `91 YJ comparison. Improvements/restricions over the years may very well have changed all this.

91 Jeep Wrangler YJ, carpet, tires, trailer hitch. yea....