For a 3 MPG average difference to be 3% it would mean you would need to get 100 MPG. 3 MPG difference when you see 22-25 MPG is 12-13%. I "believe", if my math is correct, that a 3 MPG gain over 22 MPG would be a 13.6% increase. So the 4cyl gets approx. 13% better MPG on average than the 6cyl.

To get the figure I believe you divide the difference( 3 MPG ) by the lower MPG figure( 22 ) to get the % increase. So 3 / 22 = 0.136 or 13.6%. I may be wrong on how you come up with the % for the difference but I think it is right. My head hurts.

IMO a 3 MPG difference, when the vehicles only average in the low to mid 20's, is quite significant. The only Cherokee model where the MPG difference is so minor that the 4 cyl really doesn't make sense from a MPG standpoint, at least IMO, is the TH( or if you do almost all highway - see below ).

2.4L TH = 19/25

3.2L TH = 18/25

On the non TH models it is 2-3 MPG better with the 4cyl on average. That adds up over time with what gas costs these days. While the highway MPG may only be off 1 MPG in the 4WD models( and not 3 MPG as with FWD ones )the city and average MPG is off 2 MPG. For most folks city makes up most of the driving and effects the average MPG a lot. If you do mostly highway the 6cyl may not impact your MPG as much although I would wager you could easily increase the difference between the 2 engines over the EPA rating with conservative driving.

**FWD Non TH:**
2.4L = 22/31/25

3.2L = 19/28/22

**4WD ADI Non TH:**
2.4L = 21/28/24

3.2L = 19/27/22

**4WD ADII Non TH:**
2.4L = 21/27/23

3.2L = 19/26/21

100,000 miles / 25 MPG = 4000 gallons of gas X $3.50 = $14,000.00

100,000 miles / 22 MPG = 4545.5 gallons of gas X $3.50 = $15909.25

Over 100K you spend $1909.25 more for fuel in FWD model, when gas is at $3.50, running the 6cyl vs the 4cyl if you see the EPA rated average MPG. As the cost of fuel rises over that $3.50 mark the difference increases fast as well. That is a lot of coin in my book.

Even if you drop back to the 2 MPG difference in the 4WD non TH's it is still a lot of coin...

**ADI:**
100,000 miles / 24 MPG = 4166.7 gallons of gas X $3.50 = $14,583.45

100,000 miles / 22 MPG = 4545.5 gallons of gas X $3.50 = $15909.25

**ADII:**
100,000 miles / 23 MPG = 4347.8 gallons of gas X $3.50 = $15,215.30

100,000 miles / 21 MPG = 4761.9 gallons of gas X $3.50 = $16,666.65