Worse mileage towing with 6.4 2500, than 5.7 1500?

[mohemipar]

I always tell people who ask me about fuel numbers on a gas HD that you just have to go in expecting them to “suck”, at least to 9/10 people’s standards. If you can get 17-20 on the highway then hell yeah brother and more power to ya. Personally I don’t think it’s bad for the type of vehicle you’re dealing with. But always expect an HD gasser to guzzle way more fuel down than any half ton. Rampant pretty much summed up why. Yes the engine is bigger and makes good power, but that doesn’t at all mean it will be more efficient. It is WAY more over worked than the 5.7 in the 1500, even just running around empty. Think of a 1500 with a Smart Car, literally, on top of it at all times and that is basically the extra weight the 6.4 is running around with EMPTY. All things considered, a few MPG less all around than a 1500 is pretty decent IMO. This is why the 6.4 HD is also tuned for longevity.

 

[68PowerWagon]

To anyone who has ever towed anything over 5000 lbs or so with both a 1500 & 2500 knows that the final drive numbers don't matter in this case. The towing experience is night & day different. It's all in that the components in the 2500 being bigger, thicker, stronger, heavier, etc. That's everything in the suspension, brakes, driveline and the hitch itself. Everything is just beefier. Don't forget rotating mass... tires are bigger and heavier too.

Other than interior and sheetmetal, the trucks are completely different animals. My truck weighs 7110 lbs cleaned out with the gas light on. Most commonly-optioned 1500s probably don't weigh that much while maxed-out on payload. That is why the 3/4 ton gets worse gas mileage. Very simple.

Yeah I am not sure why the OP thought he was going to get the same or better mileage. Maybe he seen some diesel numbers at some point & got confused.

 

[RoadRamblerNJ]

And nobody has ask Op what size and type of tires or inflation pressure (can't assume stock/recommended). I lost 1.5 mpg going from stock AT tire to MT tires same size. Also don't know if he's lifted, if he's in WI flats or UT hills. Lots of variables.

Not 1st, 2nd or 3rd? No Trophy!

 

[DodgeDude99]

The under carriage catching wind also contributes to the lower mpg. Look under at a 1500 it’s flat, the 2500 has a lot to catch on with the axle being further from the body & larger overall.

My ‘14 Cummins on stock tires, I can get 24-26 mpg highway doing 60-65 going from Chicago to Florida, but once you get out of Indiana that’s not really feasible. 75-80, it’s 20-22( and yes those are hand calculated).

Switching to 35” Toyo ATs, I’m 18 on the highway doing 65-70 (tire size corrected with the Edge tuner).

 

[Docpaulo]

Just drove from az to cali against some strong headwind... 12mpg hand calculated... all freeway... ouch...

Wind can make or break your mpg

 

[DodgeDude99]

^^^^oh yeah, a couple of years ago going down I57 heading into the wind (they kind of wind tractor trailers were getting dumped on their sides) the mpg was so bad I thought the tank had a hole in it as I could watch the needle move going down the road.

 

[SouthTexan]

Should have got the D if towing mileage was a big concern.

The 2500 is a more stable towing platform than the 1500 regardless of which engine is in it. If you are just towing about 8k or below then the 1500 will probably do fine, but if you are towing 8k and up on a regular basis then the HD will be a better choice in my opinion.

 

[stoney]

Soooo, aside from gas consumption while towing, is there possibly anything else the 1500 did better at while in tow?!?!
I do not think I have heard anyone actually suggest they switched from a 1/2 ton to a HD truck to actually save on some gas or even had that in mind.
I find the head wind and hills really make the 6.4 suck back the gas while in tow.....take away those 2 factors and it is not that bad really.

 

[Millnoff]

Yes hand cal. We're towing from mn to id, lots of wind and hills.

The 2500 does towing much better, that is why I bought it, and at speeds under 65 gets the same as my 1500 did. 11-12ish mpg.

When it tanks is when we go 70+ averaged 7- 7.5mpg, where my 1500 would get 10 or so on average.

Same trailer, weights, and speeds.

I wasn't expecting better, I just didn't expect that much worse. Figured with 1 extra gear in the trans, lower gears in axles, and more tq with a broader curve it would do better. Was just disapointed is all.

 

[mowin]

Once I hit 70 mph, my millage drops weather empty or towing.

 

[ronheater70]

Towed about 6800 # to the beach twice last year with my 6.4.. First tome with about 2300 miles on it, second time with about 6500 on it.. first time Mileage was about 9.5, second time it touched 13 a time or two and settled around 11.3 or so if I recall.
But for me, I try to NEVER break 70 Mph, if I do its on accident. I simply like to stay 65 MAX while pulling a camper.

 

[CMV157]

Just got a 2018 6.4 2500 after selling my 2008 CTD 6.7. I like the HD chassis and do tow fairly frequently but usually not over 10k. I went in assuming the 6.4 would be terrible on gas. And so far it is! Hand calculating the current tank I'm on but lie-o-meter indicates 13 mixed but easy driving. Dropped to 10mpg towing 3000lbs. I've heard once they loosen up they get better. I'll take anything I can get! My CTD would get 18-19 normal and 12-13 towing the same weight. Decided I didn't want to deal with the newer diesels and their over engineered emission system. Also like the manners of the gas engine. So the poor mileage was something I just knew I'd have to deal with and every time I see the difference between 89 octane and diesel it makes me feel, although very incrementally, better.

 

[East0352]

I noticed a big drop in MPG just going to wider tires. I am still averaging about 14.1 overall 15.5 hwy/12.5 city. I was doingbsome experimenting to try to figure out what impacted mileafe most and drafting off of big trucks, I waa getting 22 or better at 70 with about 2 Ram lengths between us. 19 with 3 lengths. 17/18 with 4 lengths. I did this at 75 and 65mph, too without much difference. The biggest impact we have is aerodynamics.

Also, noticed that the OP said the trailer weights changed, but did the drag from those trailers increase? The drag will hit your mpgs much harder than the weight.

 

[COAinPaso]

70+ with a trailer? Maybe the mileage is better over 80 mph with a trailer... Slow down man.


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[CMV157]

I completely understand 70+. I drive across Kansas and eastern Colorado every summer. Knowing that the Rockies are waiting ahead, depending on the speed limit in that spot, and depending on what I'm towing, I'll push 75-80! At least with my old CTD. My new 6.4 will likely put up for of a fuss!

 

[turnerje]

I have a 17 power wagon (4.10 gearing). My prior truck was a 13 Laramie 4x4 1500 5.7 with the 8 speed and 3.21 gearing. Towing my UTV on my utility trailer now with the Wagon, I get the exact same mileage. I get about 9. The 1500 obviously got better mileage empty on the highway, but not towing. They are almost identical and I’m happy about that. The 1500 got about 2-3 mpg better in town. I’m ok with that too. The 2500 is considerably heavier than my 1500. OP, I’m surprised you got that kind of mileage towing in your half ton. Maybe it was 3.55 gears.

The best I’ve gotten empty on the highway is 14.5 (65-75). That’s all via the truck computer. I know that’s not 100% accurate, but I don’t really care.

 

[pjs386]

To anyone who has ever towed anything over 5000 lbs or so with both a 1500 & 2500 knows that the final drive numbers don't matter in this case. The towing experience is night & day different. It's all in that the components in the 2500 being bigger, thicker, stronger, heavier, etc. That's everything in the suspension, brakes, driveline and the hitch itself. Everything is just beefier. Don't forget rotating mass... tires are bigger and heavier too.

Other than interior and sheetmetal, the trucks are completely different animals. My truck weighs 7110 lbs cleaned out with the gas light on. Most commonly-optioned 1500s probably don't weigh that much while maxed-out on payload. That is why the 3/4 ton gets worse gas mileage. Very simple.

As a fair comparison, my '14 1500 5.7 quad scales at 5120 unloaded - a big difference of 1990 lbs! My on the road mileage with light load steady at 70mph is around 22 mpg and when towing a 4500 lb UHaul trailer, the mpg drops to around 15-16 mpg.

 

[stoney]

On the speed topic, if I stay around 100 kpm, it is not bad, but once I go over 110, it starts to really use a lot more fuel.

 

[Docpaulo]

The best I’ve gotten empty on the highway is 14.5 (65-75). That’s all via the truck computer. I know that’s not 100% accurate, but I don’t really care.

Just came back from cali... az to cali 12mpg with headwind
Cali to az 15mpg with tail wind... although i was 300lbs heavier with stuff on top of my bed

 

[Sandbox]

In my 1500 5.7 CC 3.21 4x4, I got 8-9 mpg. In my 17 2500 6.4 CC 4.10 4x4, I get about 12 mpg with the same trailer and it does it so much more effortlessly.