I know the epa estimates are crap, But they are basically the same for the 4.6 vs the 5.4 and I drove both before I bought my 06 Screw with the 5.4. The 5.4 to me was much better driver and I was shocked at the difference in power of the 2 engines. my .02 worth.

 

I just got back from a 2000 mile trip from Boise ID to Southern Calif and back. I have an 04 Screw 4x4 with 5.4 and 3.73. When I started the trip I had 7000 mi on the truck and finished with 9000 mi. The only mods are a bed cover and k&n filter. The trip had a couple of mountain ranges up to 7500 ft and several in the 5000 ft elevation. Going down I drove about 65 MPH and got 19.5 mpg overall and coming back I drove 75 most of the time and got 18.6 mpg. The bed cover created the best improvement in mileage 1+ mpg.

 

Don't modify your truck. It sounds fine to me. A major magazine also debunks the bed cover theory. In fact, driving with the tailgate down or a bedcover installed lessens the economy. The bodies are wind-tunnel designed to operate more efficiently with the gate up and the bed open.

Spacers and other quackery are just a way to separate you from your hard earned money.

Any returns are nullified by their initial investment and at best are negligable

 

I have the 5.4 scab 4x4 with a bedcover and routinely get 17.5-18 mpg mixed driving and on long highway trips I'll set the cruise at about 73 mph and get over 20 mpg. I think the thing that helps me is the 3.55 gearing. It's not exactly quick off the line but there's enough power in the engine when I need it to get three horses and their gear moving with no problem. The skinny 235/75R17 Hankook tires they put on at the factory probably help too, but I'm willing to give up a little fuel for a bigger footprint with my next set of tires. All the things that make trucks look so good like bigger wheels, tires, lifts, etc. really add up to drag down fuel economy. I learned the hard way with the Jeep Wrangler I traded in for my 150. I could trade in my truck and get something with better gas mileage, but with it being as good as it is, I just chalk it up to cheap life insurance. If I was to have a collision with a Prius or Mini I could probably walk away from it unharmed, but I couldn't say the same about the people in the little car.

 

The higher the price of gas, the lower the fuel mileage seems to be! coincidence, I think not!! 20.00 doesn't fill the tank, nor will it in a truck, but the mods cost nothing, RIGHT. It just may be how you drive, where you drive. comparing mileage with someone who lives in the midwest, to someone in the city, or hills, or mountains is silly. It's really comparing apples and oranges. Ask for local mileage estimates. And if you don't like the mileage,... you did buy a truck. You could trade it.

 

Man I could not have said that better! Well put! That perspective needs to be spread all around here and other forums.

 

So true about the gearing and skinny tires helping the economy. There are these and so many other factors involved in how people get such different fuel economy numbers with the "same" trucks.

 

On my last fill up I got 19.5mpg and was happy to see that. That was with 95% highway and 5% city.