I am new to this forum so I am not sure if this has been addressed yet. Is the new low sulfer diesel fuels the cause of poor fuel mileage?

or is it the emissions on the new 6.7? Just trying to understand why these new trucks are getting such poor mileage

Any clarification would be appreciated

 

emmissions are too restrictive

 

thanks mnmlod, when you installed the 37's how much did you loose in MPG. I want to put 37's on as well

 

I think some of the mpg loss may be due to the fact the new motor is .8L larger and makes 25 hp & 40 LBS TQ more than the old motor. I think most times when you add power and cid you may lose some mpg just a thought as most everybody else doesnt seem to take this in to account.

 

I've heard a lot about the 07 and up class 8 trucks with DPF's meeting these standards actually getting a lot better mileage, 7, 7.5 mpg being commonly reported, than the Oct 02 thru Dec 06 trucks. Which would be a good thing as my 06 currently averages 5.9 mpg. I doubt they'll ever do better than the pre Oct 02 class 8 trucks. I had one of those averaging 7.5 mpg. Seemed like the peak of engineering for good economy on class 8 was the early 2000's engines. Not sure if that applies to our ISB's. Don't understand why these 6.7 Rams are doing so lousy when they say the class 8 DPF engines are doing so much better than 06's. It just doesn't make sense. One would think over time they'll improve the design on the new ISB's though and get better economy as a result.

 

I don't think it is the ULSD. The main station my father and I both fuel up at in town recently switched from LSD to USLD. His '05 5.9L has showed NO difference in fuel mileage when running a tank of LSD versus running ULSD. On longer trips the past few months we have filled up at a variety of truck stops across the country, some with LSD and some with ULSD. We have seen no difference in fuel economy then, either. I think the ultra-conservative emmissions equipment on this truck is choking it and making it have to work harder than it is capable of.

 

My buddy just picked up a new pro star and would disagree as he is only getting 5.5 mpg hauling light.

 

I got the same mileage for 14 years with my old truck. SD, LSD, and ULSD. As mentioned, emissions gear on the 6.7's is part of the problem plus, there is always a trade-off for displacement and horse-power too.

 

As I posted before, I'm actually getting mpg near my 06' 5.9. Maybe 1 mpg average difference. I sure expected worse.

Considering the increased HP and torque IMHO a pretty good trade off. I'm convinced the new auto tranny helps fuel consumption somehow.

New truck, interstate 17 mpg, light towing (5K#) 13.5 and heavier towing (12K#) maybe 10 to 11.

I'm not complaining.

 

Wow that's some really crappy mileage especially for such an aerodynamic truck. I can do 6.5 on light loads but typically get 5.9 running avg gross weight 75K. I guess the industry has to hype up their mileage figures to help with sluggish sales on the emssions friendly trucks.

 

The only time increasing HP reduces MPG is when you actually use the added power. If you add a pressure box (i.e MP8 or Edge EZ) you can actually increase fuel economy unless you drive it harder, which most do, due to the fun factor.

Semi's are the same way. A lower HP truck doesn't necessarily get better fuel mileage than a 550 or 600 hp truck doing the same job since it has to work harder doing the same job.

 

The big problem with poor mpg from the 6.7 is the EGR and DPF. I've read that people who have taken off the DPF and blocked the EGR have said they improved fuel mileage up to 2.5 mpg.

 

Well, I can't really say cause they were put on the truck when I ordered it. I am getting about 14 or 15 on the highway and 10 or 11 pulling a trailer.

 

I have the new 6.7 and have done the DPF delete kit and blocked the egr too. I have seen no noticeable increase in fuel economy by removing the DPF, which really surprised me to tell the truth. But did see around 2.5 mpg increase when I also blocked the egr. I am running the Juice w/attitude also. I am becoming more and more convinced that a lot of the loss in fuel economy is due to inefficiency in the transmission. hopefully in a few months ATS will have the Torque converter ready for this truck and then we will see how much better it gets.

 

I last got 22.3 miles per Imperial gallon on a 400KM run. It was Highway . My first run on same road was 18 miles per Imperial gallon. Both runs were controlled and on Cruse Control at 110Kms/65 Miles/Hr. I am pleased with last results.