I have lockers, 5:29's, 35's, and I get between 20 and 21 driving to and from work. That's thru the hill country. The only motor mod I have is an EB RV cam. Stock exhaust, ect.

I can see an auto costing you about 3 MPG.

Granted, I have a 22re, but either way 10-15 is pretty bad. My wifes Suburban does better than that, and it weighs twice and much and has two more cylinders.

If Mad Max had a 4runner...