Originally posted by Robert
4.10s and 33" tires will get you worse mileage than your stock 30" tires with 4.10s. At least it has on my '97 4x4 SOHC. See my post at Dead Link Removed for more details, but basically I got my best mileage with 31.7" tires and 4.10s. Next was stock 30" tires with my 4.10 and my worst mileage is with my 33" tires and 4.10. Performance sucks big time now, there is no bottom end and I now turn off OD until I am cruising at or above 55 MPH. If I don't the every time I touch the gas pedal my torque converter unlocks which generates heat which is detramental to a transmission.
If you are only getting 12-13 MPG in the city then something is wrong or you have a very heavy foot when taking off. I don't race away from every stoplight (some I do) but I definately take off quicker than the average vehicle next to me. My mileage is almost always about 16-16.5 city. Depending on which tires I had on, my highway mileage has been anywhere from 17.5-20 MPG. My Explorer doesn't fluctuate very much at all between city and highway mileage like my Wife's Sable does. She gets about 15 MPG city & 27 MPG highway. Mine only varies by about 3 MPG. Since you are getting 19 MPG on the highway, that at least implies that your engine is running properly since that is what mine was rated for on the highway. The low city mileage implies a lot of heavy foot take-offs. When you have the aerodynamics of a barn, your city and highway mileage shouldn't vary by that much.