I have a budget of $10k. Is 4.6L reasonable if I'm going to mostly commute? What is average mpg difference between 4.6L and 5.4L stock? I've narrowed my search down to a 2004 FX4 with 140k miles for $11k vs a 2005 XLT supercrew for $9.5K with 140k miles as well. Both are in excellent condition and have a history of being well maintaned and cared for. I love the looks of the FX4 but the XLT seems like a more practical choice for daily driving.

 

I just sold a 97 Scab with a 4.6L, stock truck. I also have a 07 5.4 Scab with the heavy half option(4.10 rear, 8' box) also stock, and both are 2wd.
They both ended up around the same mpg around town and the 07 had a slight edge on the highway. Both were around 15 mpg in town and on the highway the 97 got almost 20 and the 07 actually got a little over 20 mpg on occassion. Even with the additional length and weight, the 07 was as quick or quicker than the 97, though I don't have a heavy foot.

If stock like mine, there's not an appreciable difference in mileage between them. If you plan to put on bigger tires, raise it etc, then the additional torque on a 5.4 may be a better choice, though either likely will lose mpg if you do.

My 2 cents.

 

Tik, not for nuthin' but research the TSBs for that year Ford. I also have an 04 fx f150 with 144K and there are problems and they will cost you $$$$$. I had the tranny rebuilt 24K miles ago and now is starting to go again, the shudders, the this the that it keeps adding up and adding up. I'm stuck with this vehicle, I highly suggest to research and research again then make your decision.
Good luck...