Mileage compared to my 5.7 Hemi

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Ryan Fransen

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Hi. I've a 5.7 Hemi 1500 and just completed my first trip with my travel trailer. Mileage without towing is 13L/100 and when towing is half at 26L/100km.

I've read diesels are ~20 more efficient than gas engines, but curious if that means with or without towing.

We're I to buy a 2500 diesel, should I expect a 20% improvement on the 26L/100km I currently get, or much better than that?

Thanks.
 

crash68

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Diesel fuel itself has 20% more energy per gallon than gas.
You definitely see better efficiency while towing with a diesel compared to a gasser. With either the biggest factor for fuel economy is wind load/speed. If your looking to tow a trailer behind a CTD that you can with a 1500, you won't even notice it behind you and the fuel efficiency increase will be more than 20%
I tow a 8K lbs trailer behind my EcoDiesel and get 14-15 mpg(16l/100km).
 

Dennis Shellito

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You made my head hurt from converting the metric measurements over to miles and gallons, but with that said here is what my thoughts are on your gas vs. diesel conundrum.

I bought my Cummins for easy towing rather than just a little extra fuel milage. If your 1500 gasser pulls your trailer well, I don't see any reason to trade it for a diesel. I used to have a 32' 5er that I pulled with my 2011 deleted Cummins and would get 12-13 mpg and after I traded my 10,000 lb. 5er for an 8,000 lb. toy hauler travel trailer my fuel milage went down to 11 -11.5 mpg. I think this is due to more wind resistance on the travel trailer. I usually pull my camper into or over the rocky mountains and the diesel pulls the weight at lower rpms than a gasser due to the torque. A Cummins reaches full torque (850-900 Lb/ft , remember my truck is tuned/deleted) at 1600 rpms, while the 5.7L hemi achieves less than half that much torque (400 lb/ft) at 4000 rpms. In a nut shell, if your truck pulls your camper to your satisfaction I would not recommend trading for a diesel, because the added expense of upkeep on a diesel will offset the added fuel mileage. I don't think a 1500 gas truck would pull my camper very well because of it's weight.
 

star_deceiver

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How often do you plan to tow said trailer? Unless it’s every 2nd weekend year round or more, stick with the 5.7.

Ever leave the island with the trailer? Plans to tow to Nova Scotia? No? Cummins probably isn’t for you.

When leaving a red light unloaded: do you like to mash the go pedal and fly and have people not cut you off and slow down? The Cummins dead pedal sucks!

Can you do all the extra maintenance that comes with a big diesel? Your local Dodge dealer will gladly take 3x the amount it would be to do it yourself... fuel filters are expensive! Out of warranty repairs are really expensive.

The Cummins trucks do their best, make sense financially, and have the least amount of problems when they’re loaded and towing full time. They’re designed to work and do that work very well.

If you’re looking for better fuel economy and don’t mind a slow to accelerate truck, check out the ecodiesel. Gen 3 seems to be doing much better than the previous. Just make double sure your payload and towing numbers of the truck will match the trailer.
 

Dennis Shellito

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How often do you plan to tow said trailer? Unless it’s every 2nd weekend year round or more, stick with the 5.7.

Ever leave the island with the trailer? Plans to tow to Nova Scotia? No? Cummins probably isn’t for you.

When leaving a red light unloaded: do you like to mash the go pedal and fly and have people not cut you off and slow down? The Cummins dead pedal sucks!

Can you do all the extra maintenance that comes with a big diesel? Your local Dodge dealer will gladly take 3x the amount it would be to do it yourself... fuel filters are expensive! Out of warranty repairs are really expensive.

The Cummins trucks do their best, make sense financially, and have the least amount of problems when they’re loaded and towing full time. They’re designed to work and do that work very well.

If you’re looking for better fuel economy and don’t mind a slow to accelerate truck, check out the ecodiesel. Gen 3 seems to be doing much better than the previous. Just make double sure your payload and towing numbers of the truck will match the trailer.




I agree with most of what you posted, but the Cummins "dead pedal" has me stumped. I can wipe the doors off of a 5.7L hemi with my Cummins, so I don't know where you are getting your info from. When my truck was tuned with the H&S minimaxx it would turn a quarter mile in a little over 12.7 seconds, and there certainly wasn't any dead pedal as you say.
 

star_deceiver

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I agree with most of what you posted, but the Cummins "dead pedal" has me stumped. I can wipe the doors off of a 5.7L hemi with my Cummins, so I don't know where you are getting your info from. When my truck was tuned with the H&S minimaxx it would turn a quarter mile in a little over 12.7 seconds, and there certainly wasn't any dead pedal as you say.

You have a tuned truck, of course yours is balls to the wall. That’s why you tuned it. I would expect nothing less.

Take a newer (stock) one for a test drive. When you mash the go pedal, from dead stops, rolling at certain speeds; The truck will completely fall on its face before deciding to move. Once it decides to go, you go. You need to plan your on-ramps carefully and learn the proper ‘slow roll on to 3/4 throttle’.
 

BubbaJo

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we have a small toy hauler (20'2" length) that we used to tow with our ecoboost (3.5L) f150. The F150 did it well enough the first two years of hauling it, but we averaged maybe 8mpgs doing 68mph on the highway. This is across michigan, which is a pretty flat state. The f150 started to turn into a money pit, and we want to upgrade campers in the next year or two, so we got our used diesel. I can tow the same camper, going faster (72mph) and i get around 10mpgs towing the same roads i did with the ecoboost. Mine is currently bone stock and i have oversized off-road tires (35s) so that kills my mileage.

If i can get the same numbers as my stepdad does with his tuned dirty max i will be happy (he gets 13mpgs with a 36' 5'er and 16' fishing boat behind him). I wont do a tandem pull, but our next camper will be a lighter weight 5'er toy hauler.
 

Dennis Shellito

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we have a small toy hauler (20'2" length) that we used to tow with our ecoboost (3.5L) f150. The F150 did it well enough the first two years of hauling it, but we averaged maybe 8mpgs doing 68mph on the highway. This is across michigan, which is a pretty flat state. The f150 started to turn into a money pit, and we want to upgrade campers in the next year or two, so we got our used diesel. I can tow the same camper, going faster (72mph) and i get around 10mpgs towing the same roads i did with the ecoboost. Mine is currently bone stock and i have oversized off-road tires (35s) so that kills my mileage.

If i can get the same numbers as my stepdad does with his tuned dirty max i will be happy (he gets 13mpgs with a 36' 5'er and 16' fishing boat behind him). I wont do a tandem pull, but our next camper will be a lighter weight 5'er toy hauler.



You don't mention what year Cummins you have, but 35" tires on a 2008 - 2017 (?) or whichever years had the 3.73/1 axle ratio makes pulling a 5er use more fuel. When you have the newer model years up through 2019 that came with a 3.42/1 as the standard gear mixed with 35" tires you are not only going to see a loss of fuel mileage but also risking damage to the transmission caused by overheat when pulling the same trailer. Thankfully, FCA came to their senses and returned their standard axle ratio back to the 3.73/1 for the 2020 model year for the 2500 Cummins trucks.

My oldest son has an 06 2500 5.9L Cummins and recently put 35.5" tires on it and pulling a fairly light travel trailer it is having overheat issues, and his truck is running 3.55/1 axle. He is seriously considering selling wheels (after market) and tires and going with smaller tires.
 

Fuel35 67

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My 11’ has 3:73’s, 35’s, 68rfe, 4x4, CCSB and lifted 4 inches. Just drove to Shandon California from Hanford California going through 3 sets of hills with flat valley in between the 3, doing 70mph and hand calculated mileage is 19.6, with the 6.7 Cummins.
 

BubbaJo

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You don't mention what year Cummins you have, but 35" tires on a 2008 - 2017 (?) or whichever years had the 3.73/1 axle ratio makes pulling a 5er use more fuel. When you have the newer model years up through 2019 that came with a 3.42/1 as the standard gear mixed with 35" tires you are not only going to see a loss of fuel mileage but also risking damage to the transmission caused by overheat when pulling the same trailer. Thankfully, FCA came to their senses and returned their standard axle ratio back to the 3.73/1 for the 2020 model year for the 2500 Cummins trucks.

My oldest son has an 06 2500 5.9L Cummins and recently put 35.5" tires on it and pulling a fairly light travel trailer it is having overheat issues, and his truck is running 3.55/1 axle. He is seriously considering selling wheels (after market) and tires and going with smaller tires.

It's in my little bio thing under my avatar ;) however i have a 2012 with 3.73s.. the 35's came on the truck when i purchased it in july. They are pretty new hence why i haven't gone 'down to 33s' yet however i have been considering it before winter and using the 35s as weight in the rear end for traction or just selling them outright to recoup some money
 

Poolman Marshall

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I have a Rockwood 2612WS TT and I was pulling it with my 2017 Ram 1500 Big Horn CC 5.7 about every 3 weeks on average. On flat ground and mild hills it pulled great but I was on the edge of maxing out my payload on every trip. If we wanted to take friends and their stuff it made me get a bit nervous. This year I purchased a 2020 Ram 2500 Big Horn CC Cummins and couldn't be happier. When I go up big hills if feels effortless. The unexpected benefit is the exhaust brake. I don't have to ride the brakes like I was having to in the 1500. I also use my truck for work and I needed the write offs. It also gets better economy than the 1500 but you get a much more relaxed drive when pulling a trailer.
 

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