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Cummins MPG

H

HomelessBound

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I'm torn between a 2500 gas and 3500 SRW Cummins (not sure if regular or HO). What kind of MPG are you folks getting loaded / towing? Please mention whether you are HO or regular and which rear end you have. Fuelly seems to be a mixed bag.
 
I haven't been towing anything yet, but I am averaging 16.665 mpg overall after 1,200 miles as measured by how much diesel I put in the truck. The truck computer estimates I have been getting 16.9 MPG, so the computer is not far off.

I have the high output engine, and I have been driving in mostly hilly areas. I did go over two mountain passes.

I get my RV in a week. I will report back with mileage numbers in a few weeks.
 
Seems to line up with what the 6.4 is getting without a trailer. The few samples in the 6.4 towing thread are showing 10-11 MPG for travel trailers so interested to hear how your RV compares.
 
Just food for thought:

Keep in mind that this is just based on gas being close in price to diesel as it is right now, and fuel efficiency of both engines being within 1-2mpg of each other.

Right now, diesel averages 3.034/gal across the US and midgrade gas is 2.924, difference is about 11.3 cents a gallon when you also factor in DEF use.

Driving 100,000 miles at 16.7mpg from the diesel as above, your cost is $18,621.
Using the 15.5mpg for the Hemi I've seen quoted in another thread, your cost would be $18,864.
You would save $242 every 100,000 miles with the Cummins.

Factor in the cost of the Cummins option, at $9000:
You break even after driving that distance 37 times. Or at 3.7 million miles.
If the Hemi gets 14mpg, you would break even at 400,000 miles.
If the Hemi gets 16mpg, you would actually lose $350 every 100,000 miles.

Plus.... your Cummins isn't going to be just $9,000. If you finance the truck at 4% for 60 months, you'll pay $1,800 in interest on it as well, raising your break even point by about 20%. If instead you pay cash for the truck upfront, then you still have interest loss because your $9k isn't sitting in the bank earning interest, in a CD for example. Current rates are around 2.5%, so you could earn around $1,100 in interest over the same 5 years. Your break even point goes up by about

No other costs differences taken into account here, such as engine periodic maintenance, fuel filters, etc.

I am not offering an opinion on which engine you should own. Just running some math.
 
Distillusion said:
Just food for thought:

Keep in mind that this is just based on gas being close in price to diesel as it is right now, and fuel efficiency of both engines being within 1-2mpg of each other.

Right now, diesel averages 3.034/gal across the US and midgrade gas is 2.924, difference is about 11.3 cents a gallon when you also factor in DEF use.

Driving 100,000 miles at 16.7mpg from the diesel as above, your cost is $18,621.
Using the 15.5mpg for the Hemi I've seen quoted in another thread, your cost would be $18,864.
You would save $242 every 100,000 miles with the Cummins.

Factor in the cost of the Cummins option, at $9000:
You break even after driving that distance 37 times. Or at 3.7 million miles.
If the Hemi gets 14mpg, you would break even at 400,000 miles.
If the Hemi gets 16mpg, you would actually lose $350 every 100,000 miles.

Plus.... your Cummins isn't going to be just $9,000. If you finance the truck at 4% for 60 months, you'll pay $1,800 in interest on it as well, raising your break even point by about 20%. If instead you pay cash for the truck upfront, then you still have interest loss because your $9k isn't sitting in the bank earning interest, in a CD for example. Current rates are around 2.5%, so you could earn around $1,100 in interest over the same 5 years. Your break even point goes up by about

No other costs differences taken into account here, such as engine periodic maintenance, fuel filters, etc.

I am not offering an opinion on which engine you should own. Just running some math.
Click to expand...

That's all good information to consider. I expect the overall cost of the diesel to be much more than a gas engine, but I like the 1,000 ft/lbs of torque, the sound, and the reliability (hopefully).
 
I have a 3500 SRW HO/Aisin with a 3.73 rear end. When towing my 10k lb bumper pull toy hauler I see an average of 11-12. That is through very mountainous terrain in Idaho.
Currently I have 2785 mi and nearly 600 mi of that has been towing. The rest has been largely in town mileage. I am averaging just over 12mpg overall.
I have seen in several places online that people are seeing 2-3 mpg jumps at 4k miles.
 
Last edited:
Distillusion said:
Just food for thought:

Keep in mind that this is just based on gas being close in price to diesel as it is right now, and fuel efficiency of both engines being within 1-2mpg of each other.

Right now, diesel averages 3.034/gal across the US and midgrade gas is 2.924, difference is about 11.3 cents a gallon when you also factor in DEF use.

Driving 100,000 miles at 16.7mpg from the diesel as above, your cost is $18,621.
Using the 15.5mpg for the Hemi I've seen quoted in another thread, your cost would be $18,864.
You would save $242 every 100,000 miles with the Cummins.

Factor in the cost of the Cummins option, at $9000:
You break even after driving that distance 37 times. Or at 3.7 million miles.
If the Hemi gets 14mpg, you would break even at 400,000 miles.
If the Hemi gets 16mpg, you would actually lose $350 every 100,000 miles.

Plus.... your Cummins isn't going to be just $9,000. If you finance the truck at 4% for 60 months, you'll pay $1,800 in interest on it as well, raising your break even point by about 20%. If instead you pay cash for the truck upfront, then you still have interest loss because your $9k isn't sitting in the bank earning interest, in a CD for example. Current rates are around 2.5%, so you could earn around $1,100 in interest over the same 5 years. Your break even point goes up by about

No other costs differences taken into account here, such as engine periodic maintenance, fuel filters, etc.

I am not offering an opinion on which engine you should own. Just running some math.
Click to expand...
Thank you for putting this info together, its great info to have.
However, I didn't buy the HO Cummins because I was under the impression it was going to save me money in the long run. I paid the $11k for the HO because towing with it is an absolute dream compared to the HEMIs. The Hemi does the job, but the Cummins was made to tow and it does it effortlessly.
I know I'm going to be paying waay more overall for the Cummins, with the cost of oil changes, fuel filters, and so on.. but it makes my life easier, and it will hold value much better as well
 
Advantages the the Cummins are definitely the weight over the front axle when towing, exhaust brake, and power available at all RPMs. Diesels are usually easier/more legal for aux tanks as well. But for me, I could probably get away with a 2500 HEMI payload, but Cummins means 3500. Costwise, as Distillusion said - I don't see it working out but the resale is definitely higher on older diesels now, sometimes more than they cost initially.
 
I've got almost 14,000 miles on mine and getting 15.5 mpg right now on Fuelly. But, I do not tow.......FWIW

Ohhhh, it is gas. My last SRW Cummins and 3.42 gears averaged about the same with towing 13,000# about 30% of the miles.
 
Cummins 2500 on the expressway got over 21! Towing 6K TT on interstates between 14 and 15.
 
Cummins 2500; Average 18.5-19 not towing (~30% city, 70% highway), 12.5 towing 11k travel trailer (37'). Only ~2000 miles, we'll see if it improves.
 
jpaeth said:
Thank you for putting this info together, its great info to have.
However, I didn't buy the HO Cummins because I was under the impression it was going to save me money in the long run. I paid the $11k for the HO because towing with it is an absolute dream compared to the HEMIs. The Hemi does the job, but the Cummins was made to tow and it does it effortlessly.
I know I'm going to be paying waay more overall for the Cummins, with the cost of oil changes, fuel filters, and so on.. but it makes my life easier, and it will hold value much better as well
Click to expand...
No worries. My post was really just a comment to @HomelessBound about mileage he's seeing and what it means. As I said in the post, it's not a recommendation on what to buy. Just an example of how the numbers run. Generally, if you have concerns about mileage in a diesel, it doesn't hurt to be aware of return on investment.
 
I have just over 5,000 miles on mine. Averaging about 16.8 based hand calc'd. I do a suburbs to downtown and back drive every day, so, a lot of stop and go. Pure highway driving is around 21. Regens really kick the MPGs way down. I'm averaging a regen every other tank or so (maybe every 900 miles-ish). Haven't towed anything since I have been tracking with fuelly.

I was averaging 15.6 in my F150 5.0, so, doing a little less than 10% better which doesn't quite cover the fuel price difference. BUT, that truck didn't work for me towing, so, kind of a moot point. In any event, I was hoping fuel cost would be close to a wash in the switch and I think it will be in the long run.

The gasser will be cheaper to buy and own, I don't think there is a lot of debating that. However, I don't agree with the math that was presented above... First... most people don't pay MSRP, you'll likely get 10% or more off of that $9100 upgrade, so, call it an $8200 option. When you sell or trade your truck, you recoup some or all of the initial upgrade cost. Unless you are purchasing the truck with the intent to never sell/trade it, the equity has to be considered as well. The higher mileage, the more gap you will see... If you are going to keep it 2 years and trade with 40,000 miles, you probably won't recover the entire $8200 upgrade... but, if you drive it 6 years and 120k, you're going to widen the gap from the same gas truck. 10 years and 200k, and the truck is probably worth more than $8200 more than the same gas truck. Certainly you will have spent more maintaining it, but, you don't need to drive it millions of miles for it to make sense. Not a whole lot of people looking to spend good money on a gasser with 200,000 miles while the cummins is still chugging along for many more miles and has a ton of value left.

Beyond that, there is a "want" factor than no one can figure out for you. I went with the cummins because I wanted it. A gasser would have worked for me, but, I am paying for it and I am the one that gets to make that decision.
 
The want question is the one we all have to answer. For me, I wanted one rather than needed one 20 years ago. There was a time when I needed one for towing. Today I neither want nor do I need one.

But if you want or need a diesel.....nothing else will make you feel like the Cummins does. My opinion is, the Cummins is the best of the diesel world!
 
1500mi and around 19+mpg. Haven't towed with it yet. 40/60%hwy in a 2500 w/3.73s. Better than my Frontiers 17mpg and way more comfortable! I went diesel cuz I wanted it and I could. Its got so much power, I can't complain at all! Love driving it everytime I get in it. My JKs POd, but it will have it's time when the weather gets better.
 
I’ve owned 6 Dodge/Ram with a Cummins engine. ‘92 2500 LB 4x4 manual transmission, ‘06 2500 CC LB 4x4 manual transmission, ‘12 2500 CC LB 4x4 manual transmission, ‘14 2500 CC LB 4x4 manual transmission, ‘17 3500 CC LB 4x4 automatic transmission, ‘19 3500 CC LB 4x4 automatic transmission. Except for the ‘12, their mileage for highway driving was 18-19 mpg. Mixed driving was 15-17 mpg. The exception, the ‘12, got almost 2 less mpg than the others. The last three are the ones that I did a lot of serious towing with. Average mpg towing has been about 10.5. I tow a 36’ fifth wheel that loaded weights about 13.5K. My observation is that the Cummins‘ mileage keeps improving up to 40 to 50K miles, then levels off. I only have 3650 miles on the ‘19 and 1500 miles of that towing. 8DF9C22B-8C4F-419E-A03A-2660B5E9852F.jpeg
 
thestuarts said:
I haven't been towing anything yet, but I am averaging 16.665 mpg overall after 1,200 miles as measured by how much diesel I put in the truck. The truck computer estimates I have been getting 16.9 MPG, so the computer is not far off.

I have the high output engine, and I have been driving in mostly hilly areas. I did go over two mountain passes.

I get my RV in a week. I will report back with mileage numbers in a few weeks.
Click to expand...
What size tire and what rearend
gears do you run?
 
I just did a trip of about 220 miles. I drive between 60 and 65 depending on traffic. I have a 2022 laramie 2500, crew cab, 4x4, 3.73 gears, standard output cummins, 6.4 bed, stock 18 inch wheels and tires. During this trip I averaged 23.4 miles according on the trip meter. I have about 2k miles on the truck.
 
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