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Excessive fuel consumption while towing?

RamMike7

RamMike7

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I got to tow with my new 6.4 Hemi for the first time, now granted this is the first hemi i have owned since i have always purchased cummins power plants. Anyhow, my 1st trip with our 30' 9500lb. 5th wheel traveling here in Missouri with mostly flat with a few rolling hills and keeping my speed around 62 mph netted me a whopping 6.3 mpg! If we go out west with this thing im afraid to even guess how bad it might be. I expected the Hemi to not do as well as the cummins, but not quite this bad. As far as power, im actually impressed with the hemi's performance with the 8 speed, but 6mpg towing is a shocker to me, and my wife is giving me hell about it also. Could there be something wrong with the truck?
 
MtnRider said:
Seems about right for a gas truck towing a 5th wheel (from my experience). I've seen claims of much better but I'll blame common core math skills for those....


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Well, my math is fine... Recently drove from Florida Panhandle to St Louis and back - did some 1900 miles towing 31ft Cougar 5th wheel. Towing average was 10.9 mpg, both on the gauge and calculated from mileage and receipts. I think 6.5mpg is low, not about right. Personally I try not to be a leadfoot, but I still try to keep it at or around the speed limit.
 
Limey said:
Well, my math is fine... Recently drove from Florida Panhandle to St Louis and back - did some 1900 miles towing 31ft Cougar 5th wheel. Towing average was 10.9 mpg, both on the gauge and calculated from mileage and receipts. I think 6.5mpg is low, not about right. Personally I try not to be a leadfoot, but I still try to keep it at or around the speed limit.
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I would be happy with 8 to 10, and i dont drive with a lead foot either.
 
I may be way off base here as I don't tow a 5th wheel, but I've noticed significant differences between similarly weighted TTs but with very different front profiles. I always see either length or overall weight of 5th wheels when these discussions pop up, but are they all built with the same aerodynamic profile?
 
I had a 2015 2500 with the 6.4 Hemi, 6-speed trans and 3.73 rear end. I pull a 37’ 9000 pound travel trailer all over Missouri, Kansas, Arkansas, Iowa, Minnesota and NEVER got any better than 8 mpg. That was traveling at 65 mph.

I traded it in for a 2021 3500 dually 6.7 Cummins and now get 10-11 mpg towing the same trailer.

I don’t have any experience with the 8-speed transmission, but your 6.3 mpg is close to what I experienced. I hated the fact that every 130-150 miles I had to fill-up.

My 2015 did a fine job towing the trailer. It just couldn’t pass a gas station.

I liked the 6.4 Hemi, but I LOVE the 6.7 Cummins.

(I hand-calculate all of my mileages. The computer has always been very optimistic.)

Sent from my iPhone using Tapatalk
 
have you verified your trailer wheels / bearings / brakes are all in good operating condition? I am fighting poor mileage towing my boat, should be better than it is from what i've read. I did find some brake issues that i've addressed but have yet to tow to see if it made a difference.
 
Did you travel highway? Accelerating all that mass sucks a lot of fuel.
I've gotten about 1mpg better by traveling on the highway vs 2 lane roads and all the speed changes that comes with it.
 
Slow down if you want better mileage, you're basically pushing a tall square box against the wind. While you're driving, open the window and stick your hand out and hold it against the wind, now imagine how much more wind pressure a brick behind you gets.
Posted speed limits are max speeds, you can drive slower than that you know.
 
I just drove from Pittsburgh to Myrtle Beach and back last week with a '21 4.11 Cummins S.O. and averaged 8.4 to 8.8 MPG per refill every time. So I spent around $8K over your 6.4L to get 2 MPG better with my 13K LB Reflection fifth wheel.

So 1400 miles divided by 6.3 MPG is 222 gallons at a .30 cent savings on the initial 159 gallons that I had to buy (average of what I saw compared to diesel) at the gas pump saved around $47. Then you had to buy an additional 63 gallons at around $3.25 a gallon for a cost of $204.75 minus that $47 you saved for a total added cost of $157.75 for the same trip.
My truck....1400 miles divided by 8.6 MPG 159 gallons.
 
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Lary0071 said:
I just drove from Pittsburgh to Myrtle Beach and back last week with a '21 4.11 Cummins S.O. and averaged 8.4 to 8.8 MPG per refill every time. So I spent around $8K over your 6.4L to get 2 MPG better with my 13K LB Reflection fifth wheel.

So 1400 miles divided by 6.3 MPG is 222 gallons at a .30 cent savings on the initial 159 gallons that I had to buy (average of what I saw compared to diesel) at the gas pump saved around $47. Then you had to buy an additional 63 gallons at around $3.25 a gallon for a cost of $204.75 minus that $47 you saved for a total added cost of $157.75 for the same trip.
My truck....1400 miles divided by 8.6 MPG 159 gallons.
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Way to make us feel worse!

Sent from my moto z3 using Tapatalk
 
Lary0071 said:
I just drove from Pittsburgh to Myrtle Beach and back last week with a '21 4.11 Cummins S.O. and averaged 8.4 to 8.8 MPG per refill every time. So I spent around $8K over your 6.4L to get 2 MPG better with my 13K LB Reflection fifth wheel.

So 1400 miles divided by 6.3 MPG is 222 gallons at a .30 cent savings on the initial 159 gallons that I had to buy (average of what I saw compared to diesel) at the gas pump saved around $47. Then you had to buy an additional 63 gallons at around $3.25 a gallon for a cost of $204.75 minus that $47 you saved for a total added cost of $157.75 for the same trip.
My truck....1400 miles divided by 8.6 MPG 159 gallons.
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That's very interesting (thanks). So the $8k premium gets you an $.11/mile savings in fuel alone (1,400 miles divided by $157.75). And it will take about 72,000 miles to pay for itself? (If I understand correctly) ........................But it will also get you much more on resale (maybe $5k?). I'm beginning to think the diesel is the better cost option
 
pinkerton81 said:
That's very interesting (thanks). So the $8k premium gets you an $.11/mile savings in fuel alone (1,400 miles divided by $157.75). And it will take about 72,000 miles to pay for itself? (If I understand correctly) ........................But it will also get you much more on resale (maybe $5k?). I'm beginning to think the diesel is the better cost option
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I also had a 2019 Ram 2500 CC/SB 4x4 6.4L that averaged 12.5-13 MPG doing my work commute of right around 250 miles a week. Now with the 2021 3500 dually CC/LB 4x4 6.7 S.O. I am holding a pretty steady 17-17.5 MPG doing that same exact 250 mile per week commute. That will also help chip at your 72,000 mile number for an earlier pay off.

To do math...
The 2019 at 250 miles divided by 12.5 MPG = 20 gallons per week at $3.25 a gallon for $65 a week for fuel.
The 2021 at 250 miles divided by 17 MPG =14.7 gallons per week at $3.55 a gallon for $52.20 a week for fuel.

So in a year (52 weeks) I save $12.80 a week or $665 a year just counting the work commute. Then I suppose you could extrapolate it out further and assume 40 miles per week of "pleasure use". As you keep playing with the numbers it starts looking like in 5 years or so you would be out of the red for buying the diesel.... but I've never owned a vehicle more than 3 years, so I'll never get there. But as mentioned. resale price on a diesel is usually MUCH higher than a gas engine truck.

Where I believe a person really takes it in the pooper is with high trim level purchases and looking at the 12 year residual value. Buy a $52K tradesmen and a $85K Limited today and run both for 12 years and 180K miles and go to sell them. The sell price on that Limited is going to be just slightly higher than the Tradesmen. The $35K I spend extra for my Limited Longhorn will slowly vaporize as the machine ages out and the once cutting edge technology becomes outdated and ordinary.
 
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