Why does my MPG suck so bad?

[Skooter76]

Maybe they accidentally gave you the 6.4L hemi.

Yeah, those are my numbers on my 6.4

My 6.4 is just under 10,000 now and mileage has improving each tank. My daily commute is 64 miles round trip and I'm getting over 17 mpg now with speeds between 35 and 65. Yesterday the Average Fuel Economy meter was at 20.5 when I got home. I filled up this morning and got 17.2.

 

[duallyben]

True and salient point for most traditional ST rated tires (technically ST is rated to 65MPH) but many modern tires, including the Goodyear Endurance I run on everything, are rated higher. 87MPH for the GY's. Not that I tow that fast...

Endurance is one of the few that allow that speed, but you are correct. The 10 pl is what eliminates them for me, I find the saliun s637 14 pl to last longer and be more resistant to flats. Max speed is 75 mph or 120 km/h in my neck of the woods which is still faster then I like to push. Everybody has different needs with trailers and so different tires work better.

 

[El Toro Blanco]

My 6.4 is just under 10,000 now and mileage has improving each tank. My daily commute is 64 miles round trip and I'm getting over 17 mpg now with speeds between 35 and 65. Yesterday the Average Fuel Economy meter was at 20.5 when I got home. I filled up this morning and got 17.2.

What axle gear ratio are you running? Thanks.

 

[Dan50]

I have about 3,000 miles on my Cummins 2500 now. I am getting around 14-15mpg normal driving and when I tow my 9,000 TT I getting 8.5mpg at 75mph. This shocked me! I thought I would get better mileage than this.
I took a 1600 mile trip up north and back and was filling up 2 hours of towing. Is this what you guys are seeing as well?

Stop towing at 75 MPH.

 

[Brutal_HO]

Endurance is one of the few that allow that speed, but you are correct. The 10 pl is what eliminates them for me, I find the saliun s637 14 pl to last longer and be more resistant to flats. Max speed is 75 mph or 120 km/h in my neck of the woods which is still faster then I like to push. Everybody has different needs with trailers and so different tires work better.

Again, full agreement. I decided against the Sailun, which I do recommend to those with heavier RV's, for my load requirements and partly for availability OTR. If I was running a heavier or commercial trailer they would be a top contender, as would many 14 ply.

I'm of the mindset that a substantial change to the unsprung mass without also upgrading other components poses a risk of damage to the frame, springs, etc. and that even at lower pressures, those stiff sidewalls are heavier tires are going to beat the suspension and trailer to death. These things are already a rolling earthquake. The GY gives me ~900lb excess capacity per tire, more than the wheel is rated. FWIW, I picked up a nail in one and it held 40PSI until dismounted for repair.

 

[Skooter76]

What axle gear ratio are you running? Thanks.

3.73.

 

[Yeasty McFlaps]

Around 60-65 will net you the best millage i get about 19-21mpg empty and the loaded is relative to the trailer weight i have seen 14-15 with my dumptrailer weighing in at 7k and 9-10mpg with my 10k 5th wheel….it does get better with time i have about 20k miles on the truck it has gotten better over time and should get even better when the warranty expires and i go full delete on it

Same here. Almost exactly

 

[thrust]

I filled up earlier this week and have since recorded about a 3MPG drop from the previous tank with no change in my driving conditions.


Sent from my SM-N986U1 using Tapatalk

 

[CdnHO]

Fuel mileage just running arround town gets better with each fill up. Hand calculated 13.8, 14.8 and today 3rd fill up got 16.6 miles to US gallon. Truck display was blowing sunshine up my ass with 18.3. LOL Old truck (2003 dually HO 6 speed manual with 4.10 gears) running solo around town got around 15.5 on average hand calculated. So I am please with fuel mileage so far. Be interesting to see what I get towing my 21K fifth wheel. I do drive conservatively and truck is totally stock.

 

[H3LZSN1P3R]

Fuel mileage just running arround town gets better with each fill up. Hand calculated 13.8, 14.8 and today 3rd fill up got 16.6 miles to US gallon. Truck display was blowing sunshine up my ass with 18.3. LOL Old truck (2003 dually HO 6 speed manual with 4.10 gears) running solo around town got around 15.5 on average hand calculated. So I am please with fuel mileage so far. Be interesting to see what I get towing my 21K fifth wheel. I do drive conservatively and truck is totally stock.

Really i find hand calculating my readout is almost spot on or saying less than im actually getting due to idling

 

[CdnHO]

Really i find hand calculating my readout is almost spot on or saying less than im actually getting due to idling

I found my 2003 was somewhat optomistic as well. One would think that with all the electronics the truck display would be consistently accurate. Good thing the truck is not an airplane. LOL

 

[H3LZSN1P3R]

I found my 2003 was somewhat optomistic as well. One would think that with all the electronics the truck display would be consistently accurate. Good thing the truck is not an airplane. LOL

My 05 is really off usually says 19mpg it gets about 13-15 on avg

 

[Myfast70]

should get even better when the warranty expires and i go full delete on it

It's crazy how much the Def chokes and kills mpg on these trucks! I want to do the same thing too with mine once the warranty is up. Banks was talking about tunes that work with the Def in place and you pick up power & mpg still so I may look into that too

 

[gimmie11s]

Just finished a 2509 mile trip from SoCal to Yellowstone and back over 9 days. DRW Megacab HO 4x4 with 4.10 gears averaged 8.7 mpg pulling about 12k lbs 70-75 mph average (80 mph speed limit in much of ID, UT, and NV!).

I chewed through a good amount of DEF on this trip too... about 5 gallons.

We caravanned with 2 other groups all pulling similar loads to me--1 was a 2015 Cummins 2500 who averaged about .3mpg better than me (similar load to me but he had 35" tires) and the last guy was in a 2019 F250 powerstroke that averaged almost 1mpg better than me, although his truck had 3.55 gears and he was a bumper-pull 32' RV whose truck/trailer combo was about 2500 lbs lighter than me.

 

[H3LZSN1P3R]

It's crazy how much the Def chokes and kills mpg on these trucks! I want to do the same thing too with mine once the warranty is up. Banks was talking about tunes that work with the Def in place and you pick up power & mpg still so I may look into that too

Def does not choke anything thats the DPF system that does that,

 

[Myfast70]

Def does not choke anything thats the DPF system that does that,

Well ok smart ass, I think most knew what I meant... the DEF fluid is part of the DPF system, either way use of the DEF fluid and all of the other bull$hit that goes with it costs both power & MPG

 

[Epsilon Plus]

If you put a little axle and wheels on a russet potato, stuck a 7-pin into it, and plugged it into the RAM, the Cummins would get about 10MPG average.

Tow 6,000? 10MPG

Tow 16,000? 10MPG

Tow 16oz? 10MPG

Cummins DGAF. 10MPG.

 

[H3LZSN1P3R]

Well ok smart ass, I think most knew what I meant... the DEF fluid is part of the DPF system, either way use of the DEF fluid and all of the other bull$hit that goes with it costs both power & MPG

No DEF is part of the SCR system not the DPF system the only thing they share is the exhaust pipe connecting them…. Also deleteing does not net much extra mpg 1-2mpg at most the power increase is what the delete is about

 

[Myfast70]

No DEF is part of the SCR system not the DPF system the only thing they share is the exhaust pipe connecting them…. Also deleteing does not net much extra mpg 1-2mpg at most the power increase is what the delete is about

Someone read a shop manual

Hmm, that's kinda funny as I know at least 6 people that have made the switch and all have picked up a minimum of 3-5mpg and then the additional power levels & tow modes.

Done debating, you are definitely smarter than me, I give up Mr Sniper sir