Seriously, keeping your foot out of it's the best thing you can do. Driving habits have a bigger effect on MPGs than any add-on you can put on.

Keeping your foot out of it, coasting to stops, and not speeding would mean the difference of 2-3 MPGs, which is more than any mod can get you. Don't feel bad about the 5.4, though...my '03 4.2L V6 didn't get any better than my 5.4 does.

 

Environmental conditions will account for alot. Rough road surface, roling hilss, etc. Or he could be in the frozen north, or at altitude, while you're in Hawaii. Heck, If I were your truck in Hawaii, I'd be pretty happy and deliver 20 mpg too! Besides, I thought the speed limit was only 60 mph in HI?

 

Is this not recommended? and why? How inaccurate is it?
Steve

 

Binghamton NY to Hazelton PA and back through the mountains of PA on route 81. Yes it's North and yes it's Frozen. As for Hawaii, when as anyone actually gotten up to 60mph there? 2 million people in the greater Honolulu area and three highways. Do the math. [Edit, this is a 4 wheel drive exteneded cab]
Second edit: I don't have an information center, and I use the same pump at the same station for consistant results.

 

It varies. I've seen them within a few tenths of a MPG before, and I've seen them off by 2-4 MPGs as well. They're great for comparison, or a good estimate on what MPG you're getting RIGHT NOW, instead of an average over a tank.

However, if you calculate it tank-to-tank, it will be nearly 100% accurate, with the only possible discrepancy being exactly how full you can get your tank...

And if you calculate it over time, adding the mileage as well as exactly how much gas it took at each fill-up over a month or two, it will be darn near perfect.

 

I haven't always lived in Hawaii
Hawaii speed limit is 35 mph statewide (pretty much)...with a 55 mph highway and about 10 miles of 60 mph.


I currently get 12.5-13 mpg consistently no matter what I do...there is no "Highway" driving to speak of here



that 20 mpg I'm talking about was on the Mainland. From Seattle to Denver to Austin and back I consistently got 18+ mpg at 75+ mph. When I got to Kansas (I-35) and had to slow down, I got 20+ mpg.




Crazy said it best. The absolute biggest factor for MPG is the driver. Drive consistently and easy on the throttle...use CC, keep your tires aired properly and