Real world 2024 Gas V/S Diesel Fuel Economy

The diesel is a lot more money up front.Gas will get way worse mpg towing or not.The biggest issue i would have with the gas motor is losing the exhaust brake towing.

How big of a camper? How many miles a year will you drive? How many of those miles will be with the camper?

The diesel 'should' deliver better fuel mileage but, if you read around on here some with the new style truck do well, some don't at all. New trucks are heavy, aero bricks, the diesel can erase that feeling since it has so much power, but that means fuel.

Dave Brabec said:

The diesel is a lot more money up front.Gas will get way worse mpg towing or not.The biggest issue i would have with the gas motor is losing the exhaust brake towing.

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That would be my concern as well.

To the OP, have you previously had diesel trucks?
I would say if you are used to owning a diesel, get a diesel. If you are fresh to the truck and trailer thing, get the gas. Cheaper, easier and you won’t know what you’re missing.

If you are only towing 2-3 times a year, i'd go with the gas.

IMO Too new of a combination to answer that question, especially not know the size of the trailer you plan on getting.
Since my 2021 duramax got a new ECM flash from the dealer, it’s getting even better fuel mileage mid 20mpg Canadian driven at the speed limit.

If your serious about a gas HD truck look at ford with the big block V8 in it, very impressive engine and its really good on gas, my buddy has one in a SRW 350 and he’s claiming very good gas mileage.
My 15000lb service truck has that V8 gas in it. The guys in the fleet that have the 6.6 gas GM with the 6sp with SRW are not that impressed with them.


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If all I ever intended to tow was my own camper and it was anything other than a huge 5th wheel, I'd still have my 2021 with the 6.6 gas. But since my intent was to get back into more commercial towing, I traded it for a dually diesel. Hooked onto back to back triple axle 15k+ 5ers in the mountains back east last week so that's why I have a diesel.

My gas Chevy got about the same mileage empty as the Duramax trucks I've owned. Towing mileage was about 10-20% lower than diesel. I could tow my personal 26ft 5th wheel and get 8-9mpg. My diesels got 10.

I really liked my 6.0 GMC but the 6.6 was noticeably more powerful and got better mileage. I really liked it. Wish I could afford 2 nice trucks.

I would never believe anyone that says they get 20+ mpg with their Duramax diesel in a 2500 or 3500. I had a 2019 3500HD and got 15-16 not towing and 8 towing a 28’ enclosed trailer. I put 22,000 miles on it making 13 round trips when I moved. It didn’t matter if the trailer was loaded or empty, the mileage was the same. I completed my last trip on October 31 and traded it for a gas on November 1. couldn‘t trade it fast enough. I have a 22 Denali now and a 24 Denali that is in transit. Couldn’t be happier with the 6.6 gas and with the 10 speed it will be even better.

drewallendennis said:

Does anyone have any real world data on the 2024 6.6 Gas V/S 6.6 Diesel fuel economy. Going next week to order my truck, and I'm seriously torn on which to get. A camper is in my future plans. Outside of that I won't be towing much. Majority of the driving will be less than 2 hours, with occasional 500+ mile trips. I know short trips aren't the best on a diesel since they don't have time to get up to temp. I've got everything settled except the powerplant debate. Thanks for your input and opinions!

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Like some others have asked, what size travel trailer or fifth wheel you looking at?

Personally, If I was towing within 70% or less of the trucks towing capacity range and doing just local campgrounds with the occasional 500+ mile trip I would most likely consider the 6.6 gas/10spd. Towing heavy with a gas will not be as relaxing as towing heavy with a modern day diesel.

Gas offers no def or special emissions, doesn't really care about short trips to the store. Gas prices are usually lower than diesel prices and I think this would most likely negate the MPG difference, especially if most of the driving is not towing.

Caper11 said:

first one is a actual trip US MPG, second is my DEF tank distance. If you know how to do math you can convert them to Canadian MPG like I said In my previous post. Add 30km or 19 miles to the trip 1 because I forgot to reset it after I fueled up yesterday.
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Caper do you verify with hand calc as well? I'd be interested to see the variance in your DIC. On my 2017 I am consistently 1 mpg than the DIC's numbers. So even with 1 mpg low, you're getting fantastic mileage.

Caper11 said:

first one is a actual trip US MPG, second is my DEF tank distance. If you know how to do math you can convert them to Canadian MPG like I said In my previous post. Add 30km or 19 miles to the trip 1 because I forgot to reset it after I fueled up yesterday.
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Very adult emoji there. Keep up the good work!

Satar said:

Like some others have asked, what size travel trailer or fifth wheel you looking at?

Personally, If I was towing within 70% or less of the trucks towing capacity range and doing just local campgrounds with the occasional 500+ mile trip I would most likely consider the 6.6 gas/10spd. Towing heavy with a gas will not be as relaxing as towing heavy with a modern day diesel.

Gas offers no def or special emissions, doesn't really care about short trips to the store. Gas prices are usually lower than diesel prices and I think this would most likely negate the MPG difference, especially if most of the driving is not towing.

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When I got the 2020 gas truck, it got terrible mpg towing. The cost wasn’t necessary the problem, it was the frequency of stops.

When it comes to mpg, newer trucks vary big time. No two truck is created equal. I think average mpg ranges from 14-20. I am not happy with my 2017, as I came from Cummins trucks that would get 20-23 mpg on the highway. I think the worst mpg average I got in a Cummins was 16.5.

I went away from gas to the dmax, not my 2500 was a 16' 6.0 gasser. The new 6.6 gas seems to be a step up from that motor. But going to the dmax I doubled my towing mpg and my unloaded highway and city mpg has increased as well. So far I have been getting diesel cheaper then gas which has been great. The towing experience is amazing and the power is awesome. I do most of my camping runs to the mountains and lots of my trips are 800-1200 miles, last year we did 13,200 miles with the camper on the gasser. We did some trips further into the mountains and boy did it work the gasser, I have 1 trip on the dmax to the mountains so far and it was night and day difference.

I’m of the opinion the gap is closing with each new model refresh when it comes to MPG’s of gas vs diesel. I’ve owned a 2016 LML, ‘19 L5P, and now a ‘22 L5P. With each of these the MPG dropped as I advanced through the models. Judging by this trend, the ‘24 probably came down a hair as well. Empty on the highway the diesel will get good mileage. For me this is not a frequent scenario. Towing my FW(12k) I rarely get north of 10mpg. Usually 9.5ish hand calc. I’d imagine a new 6.6 gas wouldn’t be much less. Mixed driving around town I’m at 13ish which is about the same as a 2016 6.0 gasser I owned.

If buying solely for efficiency the gap is tight. There’s enough advantages with the diesel that I’m ok overlooking this. But, that’s me.

On a side note, a good friend recently got a ‘22 F350 SRW Diesel. His MPG’s hand calculated are much better than my Chevy, but he had to buy a $90k Ford. So there’s that.

20 mpg with a newer 2500/3500 is possible, it just takes a bit of work and paying attention to how your driving. Not towing, my 22 dually can get 20 to 22 US (hand calc although the dash is within .2 usually). If I want to drive 75-80 or beat everyone to the next stoplight, I can easily achieve 12 mpg US also! Some trucks and drivers can do 20, some don't. As fussy as the emission system can be nowadays, I think it explains more than a few of the one's that don't.

So to say no one is believable or it's impossible to get 20 is just flat out not true.

Hopefully the OP comes back and answers some of the usage questions asked.

Piper One said:

20 mpg with a newer 2500/3500 is possible, it just takes a bit of work and paying attention to how your driving. Not towing, my 22 dually can get 20 to 22 US (hand calc although the dash is within .2 usually). If I want to drive 75-80 or beat everyone to the next stoplight, I can easily achieve 12 mpg US also! Some trucks and drivers can do 20, some don't. As fussy as the emission system can be nowadays, I think it explains more than a few of the one's that don't.

So to say no one is believable or it's impossible to get 20 is just flat out not true.

Hopefully the OP comes back and answers some of the usage questions asked.

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I agree 100%, if you have the right truck. Some trucks just can’t do it.

@Mattswaggs , I just need to send you some of my maple flavored fuel additive. 😜

I generally get 13.5 driving around town