Does anyone know or care to guess how much lower the MPG would be with the 3.92 axle ratio option compared to the 3.21 ratio that is standard (and probably used to come up with the 17/22 MPG numbers)?

My '92 318 4X4 gets about 14.5-15 mpg with the 3.90 gearset. Runs about 2300 rpm at 65-70 mph with P235/75R15s. Are the 3.21s you are talking about available on the current Dakota's? I thought you could only get 3.92s or 3.55s. Or are you considering swapping the 3.21s in yourself?

The 3.21 comes standard on the 2004 Dakota. You have to pay $40 extra for the 3.55 or 3.92. I'm looking to buy a new SXT now but it has the 3.92 and I don't want to pay a large penalty in MPG. 1-2 MPG would be ok but 3-5 wouldn't be worth it.

I just drove my new '04 Sport, 4X4, 4.7L, 5 speed manual (yes, manual!), with 3.55s and got about 22 mpg at 1750 rpm/65 mph over the 700 highway miles home. Tires are the P265/75R16s. You'd probably run 1600 rpm with the 3.21s and around 2000 with 3.92s with the same tires. Difference in mpg from the low to high gears would probably run more towards your undesired 3-5 mpg. I'm anxious to see how my mileage settles as the engine breaks in. Incidentally, my window sticker says 14 city/19 highway, so for now, I'm beating that by quite a bit. I'm told that 3.21s are standard only on 2WD, with the 3.55s standard on 4WD.