What hasn't really been said is that if you pay $800 for a propane kit to get better mileage, then you have to figure out how long it will take to pay for itself with the savings. It will only net you a gain as long as propane is cheaper than diesel. Same story for any other "mileage" add on to the truck. Some mods can legitimately improve engine efficiency. But you're only going to get so much out of a 6600lb 4x4 truck. I don't know that 30, much less 40 MPG is attainable, but I highly doubt it. If someone figures out how to do it that doesn't involve a really big hill and one halluva tail wind, pretty please fill me in on the secret.
Your driving style and the terrain you're driving on have a lot to do with it too. Going up and down hills all day will kill mileage faster than a tax reform bill in congress. On the other side of that, unloaded on flat terrain puts the least load on the motor.
So ultimately it will be different for everyone. Most guys I know would love to get 20mpg. Hell I sure would. Don't fix it if it ain't broke.
X2 on the hand calculated mileage. It's the more accurate than the DIC, usually.
A lift pump will allow your CP3 and injectors to live longer while maintaining higher rail pressure. So that could help your MPG in that the motor is more likely to get the fuel your tune calls for. I'll find out in about a week ish when I install the new AD165 I just got from Alligator Performance! (Shameless plug, I know. You guys are awesome. I've spent enough money there to **** off the wife for a while. haha )

 

Awesome You Will Like it Bud!!! As for propane with out building your own kit your not gonna get it from any manufacturers anymore that I know of. They have all been discontinued to my knowledge. You can almost do the same thing for mileage if you can take time to set up your water meth system.

 

I'm more interested in the water injection than propane. Mostly to keep EGTs down and clean out the heads. Although I will say I'd be interested in looking at a DIY for propane and water injection.
I'm pretty excited to get that lift pump on. I'm going to be ditching the stock filter setup and bypassing the FICM while I'm at it. That on top of the built trans from Mike L should definitely support some more powerful tunes. I feel so bad for my tires when those mods are done. haha
Scott, I may be hitting yall up for another boost gauge/triple pillar pod for a drive pressure gauge in the next month or so. We'll see what happens. Yall still carry Sport Comp II gauges?

 

Yes sir we can get whatever sport comp gauge you need.. Yeah Holton our Dmax tech here bypassed his fuel bowl and all that after his airdog. And yeah tires dont like all these mods!!!

 

If you bypass the FICM, how will it cool itself?? The FICM uses diesel to cool the internals, without out it, it wil fry....quickly.

 

I'll be relocating the FICM away from the motor so I'll actually be removing sources of heat from it. The engine itself and the hot fuel flowing through it. I've read on DD where several guys have bypassed/relocated it to the inside of the fender and left it air cooled only with no problems. I'll also be trying another mod Mike L recommended. I'll be adding an additional fuel cooler to the return line and cleaning the heck out of the stock one. He reported an efficiency gain just from cooler fuel. So we'll see how that goes. Hopefully I'll be able to report some gains in a month or so.
RTToys, did you have a different experience with bypassing the FICM?

 

Nope, never done it, nor do I plan to do it. The idea of cooling the FICM with fuel is not due to the heat generated by the engine (although I'm sure engine heat doesn’t help any), it's the heat generated internally from the electronics.

Removing it from it's external heat source would be nice, but you still have to dissipate the internal heat.