fuel mileage tips

Yeah that RR will hurt a bit. I have singles and a month before winter I put the XDN2 on, which have a RR of around 150 (something high) and my mileage dropped a solid .7 from the XDA energy I had on. Didn't care though cause winter was on its way.

I do not have a scangauge; I don't plan on using one either. I might not be able to see instant read out, but I do know what is required to achieve optimal mileage (studied mechanical engineering in college, which comes in handy once in a blue moon....). I had a friend use the regular scangauge and he said it was nice to see an instant, but really didn't change his driving style by to much.

In terms of not having the ability to run slower, that hurts a bit. There are pro's to running faster though (some may not agree). You will have more momentum which will keep you from having to push for 40 lbs of boost, so you won't really save any, but in turn burn a bit less (if that makes any sense). Few times I really have to hammer down, I notice my boost rarely goes above 20 because I have more momentum pushing along. You are still burning more fuel though, but you aren't burning as much (probably a difference of .25 at most). Though really monitoring your boost makes a big difference. Anytime I catch a tail wind I make sure to take full advantage of it.
Not sure about the air tabs and side skirts as I don't have them, but I'd imagine it makes a difference. Might as well put a single 50 gal tank if you want to really go all out

With a different set of gears comes a completely different truck. My dad's truck carries more power shifting at 1600 rpm (12.7L/13 spd/2.93 gears) where as mine I shift at 1250/1300 (N14 celect +/13 spd/3.73 gears). Only way it would make a greater difference would be adding more HP/TQ and dropping gears at same time (at least as far as I am aware of, hopefully someone can chime in with more info on that).

Other topics to consider:
Coasting (ie. Letting off the throttle say 1/2-3/4 mile before exit and slowly rolling to the exit OR if getting on a ramp that's downhill, let gravity be your friend and coast up to cruising speed, if you can). Don't throttle all the way to the top of a hill (go far enough to be able to coast over the top and coast to cruising speed again). Not stopping every 5 minutes. Maintain/Consistency.

 

This part in particular is what you should try to focus on when you can. I remember my first trip ever I kept my eye on the boost gauge and pyrometer (exhaust temp gauge). That trip from Mahwah, NJ to Duncan, SC I recorded a 9.361. Now I know running at 60 mph helped some, but I really made sure to monitor my boost.

 

Well yes, if you are running at 40 lbs for 1,000 miles or 10 lbs for 1,000 miles, which is more ineffective? Now you might not be the first one to the top of the hill, but the savings will add up. Ideally if you can keep the boost close to 0 you're doing great! Burning the least amount of fuel possible. Which is the goal in the long term right?

 

A 400 cummins will normally have it's peak torque 1000 rpm to 1450 or so you should be able to keep it in top gear down to 45 mph or so anything above 1450 it's wasting fuel with 3.73 you will be ideal 55 to 62 mph max it will really drink more fuel above 1450 rpm unless you run on the foot with a light throttle. If your kW has the 4 economy trip gauges I like to use one as a instant I reset it to keep track of current economy and try to keep it on the plus side as far as I can it really helps

 

Good stuff here. Agree completely. I also run 57 and consistently get high 8's to mid 9's with an occasional 10. And I idle a fair amount also. Good aerodynamics is huge too.