A reminder to you all.. Change those O2 sensors....

[EcoVan]

We've had my wife's 2007 Jeep Grand Cherokee 4WD 3.7 v-6 for about 4 years, now with about 218,000 miles. Runs great, but I read that O2 sensors get lazy over time. We may have had the original sensors. Just had them changed out and gained about 2.5 to 3 mpg. Went from 21.2 MPG highway to around 24 or more in initial tests. The only changes to the stock car is a freer flowing 2 1/2 exhaust ( really bumped up mid range and up power), back end lowered about 1 inch, most of the air leakage paths around the radiator have been closed up and the front skid plate gone ( probably bad for aero).

It sure does look like my goal of getting near 30 mpg with this vehicle is within reach with some decent aero mods. There's lots of room for improvement

Working on my 2017 Express van right now with the new lower air dam in place and have been mocking up the front belly pan. This Jeep is next.

[oil pan 4]

They not only get slower they also start to favor giving a lean signal which makes the engine run richer.
Skid plates appear to better for aerodynamics than exposed chassis parts.