You need to change your gears! If you are running 37 inch tires with 3.73, they are now acting like 3.18 for a rearend ratio. Your only choice is to change to the 4.11 since I don't think there is anything else out there. You are running out of the RPM range you should be in.

 

I was at a different dealer today b/c my original dealer $uck$ and the service guy told me to bring in my fuel receits and odometer readings so the diesel tech could look at it all. Service guy told me the Power Control Module (PCM) might need to be adjusted. Hope this works. I'm getting an average of 14.5mph each tank with a best of 15.2 with 50/50 mixed driving and average acceleration. Hope they can do something.

Jamie

 

I pull a 36ft Fifth Wheel with a dry weight of about 12,000 lbs, I was getting about 6.5-7 mpg, What is the story with the engine build date?? I ordered my 600 on Jan 30th, is there a difference in MPG?

 

Do a real fill up and DON'T use the overhead, it WILL be off. It will take a few extra minutes, but fill it to the neck! run it down, fill to the neck again, THEN hand calculate. Surprise This is the ONLY way for an ACCURATE mileage reading, bar none!!!

 

BTW, you got a ton of drag with all the mods you have done to that truck, you WILL lose mileage, you also need like 4:56 gears too but don't even know if those are available yet for these trucks.

 

That's pretty bad! The worst I've ever gotten was 8.7mpg with a weight of 31320lbs. running 70mph for 400 miles.

 

I just read on here somewhere that a guy is getting like 16 MPG pulling a boat uphill hauling A$$ and he didn't think that was aceptable. HA HA HA

 

Maybe I missed it on here somewhere...whats the pressures you are running in your 37's? Tongue weight? You might just need to air up the rears when towing to gain a few mpg.

Scotty

 

Im running 38 psi cold all around the tires say up to 50 cold.

 

Bump to 50 front 45 rear...you will be happier.

 

BTW...the load rating on those tires is only 2700 each...be carefull what you tow/haul. I would trust them a little more than that since they are BFG's, but I have no experience with Krawlers.

 

I would run all four at max!

 

50PSI cold is good without a load.

70psi rear and 60psi front is more like it with a load.

 

In a tire rated at 50psi MAX?

50 front and 45 rear works on mine, which also say 50psi max.

I could see running 70/60 on the stock tires which go up to 80psi, but not on what he's currently running.


phox

 

Oh.

I'm running the Michelin's that came on it.

Low tire pressure gives a softer ride, but mileage will suffer.