School me on my gear ratio

1st: 2.80

2nd: 1.55.

3rd: 1.00

4th: 0.69



In simple terms, how does each gear vary in mpg? I'm curious just how much mpg can vary in each gear before overdrive (4th gear).

The transmission is an automatic 42rle in a 2008 Jeep Liberty.

School me on my gear ratio