Upgrade to a diesel or not?

ObiRich · 02-23-2020, 05:38 PM

I have a question or two. I've been toying with the idea of getting a newer truck to pull our 5er with. My current one is a 2009 Sliverado 1 ton, but it's a gasser. Although it does an adequate job pulling it, the fuel consumption is pretty high (get about 7-8mpg), and the engine revs pretty high when going up grades unless I really let the speed bleed off. We live in the mountains, so we do have a fair number of long grades. So I've been thinking about getting a diesel. But that's not the only reason I'm thinking of switching. My current truck is a long bed, and I'm just getting tired of the hassles when parking "the beast." Lastly, with a diesel, we could use the truck lanes when fueling if there's not an RV lane.

So my questions are directed more to Chevy or GMC diesel owners, as I'm looking at the Duramax. First what kind of mileage do you get when towing? Second, what kind of mileage do you get in day to day driving?

Larrylane · 02-23-2020, 07:09 PM

I had a 2016 2500HD Duramax and recently purchased a new GMC 3500HD SRW Duramax. My situation might be different than yours, but I live in a rural area and not in a city which is better for a diesel than stop and go traffic. We typically put around 6,000 to 10,000 miles on our 5th wheel a year and get 10.5 miles to gallon on undulating roads and around 5-6 miles to the gallon in mountainous areas. As a daily driver we got around 19 on the 2016 and currently getting 18.5 on the 2020 with only 3,200 miles.

Last year we traveled with another couple who had a gas powered truck and they struggled to keep up in mountain areas and they also struggled getting gas at the pumps where we didn't.

We like our diesel and do not regret having it.

K_N_L · 02-23-2020, 07:51 PM

Our mileage is very dependent on our speed. IF we run in 55MPH zones it can be 10 to 11, at low 60's about 9.5, upper 60's it drops to about 9, through in a a few mountain passes and we're down in the 8's. On our last trip south, we had a 15 - 20 MPH head windwind and biodiesel for most of the day and it dropped down into the 7's for a few 50 mile average periods. My overall mileage for about 22K miles is 9.6 since owning the truck but I seldom use it outside towing. I do see between 17 - 21 for non towing. It would be hard to go back to a gas truck for any towing once you get used to the torque and low rpm's. You didnt mention your camper weight but for reference, we are typically at almost 16K with the garage and everything else loaded.

ObiRich · 02-23-2020, 08:17 PM

Quote:

Originally Posted by K_N_L

You didnt mention your camper weight but for reference, we are typically at almost 16K with the garage and everything else loaded.

We have a 2019 Hideout 262RES. If the weights are correct on the label on it, then we're probably a total of 10,000 pounds with our gear and full (or semi full) tanks. Have never weighed it yet.

roadglide · 02-23-2020, 08:32 PM

Obirich how much weight are you towing . With my 1 ton srw duramax I'm at max weight 32 k on the truck and 25k towing 8.5 is my worst pulling hills in the deep south . In SW I'm averaging 10 mpg. Cruising at 75 I get 19 to 20 . My LML2500 did about the same maybe better towing but it used half the DEF as the L5P. Somebody beat me to the same question on weight.

Roscommon48 · 02-24-2020, 12:55 AM

everyone pulling a large 5th wheel gets about 9-10mpg.

a diesel will help with the mountains and the rpms are lower when going up.

I love my short bed truck.

**JRTJH** · 02-24-2020, 07:57 AM

I don't find the "towed weight" to be a significant factor in mileage while towing. I typically get around 10.5-11 MPG towing our Cougar XLite behind the truck. If I double tow/triple tow the boat behind the Cougar (about 2000 pounds) mileage remains about the same. If I tow the Slingshot on its trailer (about 3000 pounds) mileage also seems essentially "unaffected" by the added weight.

What I do notice will affect MPG, is any "wind resistance". If there's a headwind with the Cougar, the wind will affect MPG. If I tow a larger boat (weighing about the same as the Cougar), MPG will go up, probably from the "more streamlined load on the trailer". It's the same when I connect the trailer with my tractor behind the truck. It weighs close to the same as the Cougar, but MPG usually is 13-14 MPG with that trailer in tow.

I'd suspect that, within reason, it's more about "frontal wind resistance" than weight differences of a couple thousand pounds or so.

**flybouy** · 02-24-2020, 08:43 AM

Quote:

Originally Posted by JRTJH

I don't find the "towed weight" to be a significant factor in mileage while towing. I typically get around 10.5-11 MPG towing our Cougar XLite behind the truck. If I double tow/triple tow the boat behind the Cougar (about 2000 pounds) mileage remains about the same. If I tow the Slingshot on its trailer (about 3000 pounds) mileage also seems essentially "unaffected" by the added weight.

What I do notice will affect MPG, is any "wind resistance". If there's a headwind with the Cougar, the wind will affect MPG. If I tow a larger boat (weighing about the same as the Cougar), MPG will go up, probably from the "more streamlined load on the trailer". It's the same when I connect the trailer with my tractor behind the truck. It weighs close to the same as the Cougar, but MPG usually is 13-14 MPG with that trailer in tow.

I'd suspect that, within reason, it's more about "frontal wind resistance" than weight differences of a couple thousand pounds or so.

There is also a factor of "pressure gradient" that typically has a direct effect on fuel milage. The formula looks something like this.."The greater the pressure in relation to a period of time that is applied upon the accelerator by the right foot the lower the resultant fuel milage". My own theory obtained by personal observations.

Pmedic4 · 03-03-2020, 08:38 AM

Quote:

Originally Posted by JRTJH

I don't find the "towed weight" to be a significant factor in mileage while towing. I typically get around 10.5-11 MPG towing our Cougar XLite behind the truck. If I double tow/triple tow the boat behind the Cougar (about 2000 pounds) mileage remains about the same. If I tow the Slingshot on its trailer (about 3000 pounds) mileage also seems essentially "unaffected" by the added weight.

What I do notice will affect MPG, is any "wind resistance". If there's a headwind with the Cougar, the wind will affect MPG. If I tow a larger boat (weighing about the same as the Cougar), MPG will go up, probably from the "more streamlined load on the trailer". It's the same when I connect the trailer with my tractor behind the truck. It weighs close to the same as the Cougar, but MPG usually is 13-14 MPG with that trailer in tow.

I'd suspect that, within reason, it's more about "frontal wind resistance" than weight differences of a couple thousand pounds or so.

Don't have a diesel, totally agree with the major difference being 'wind resistance'. With the Cougar hanging on, I get 8-9mpg generally. I also tow a UTV, which I haul on an aluminum trailer, which fully loaded is rated at 3,000 pounds. I was really surprised by the drop in mileage with this light trailer, and at best get 9-10mpg! It has a full length loading ramp, and I'm certain the wind hitting that ramp latched at 90 degrees is the culprit. I expected it to be more in the 12-14mpg range, but no it really drops off even with that trailer.

On a RV trip of 300 miles to Branson, I expected mileage to really suffer hitting the mountains in southern Missouri, but still hit about 8-9 on the way down. On the return, heading east out of Springfield MO, surprised to see I'm getting 11-12 and thinking I'm going to make it home on one fill-up. Then once I got heading north, now the onboard gauge is saying 6-7, and now thinking I have an engine problem. Of course, I stop for fuel, and the wind out of the north now is blowing 20mph, so I see the difference.

Wind definitely is the deciding factor, and so far I've not traveled 'Where the winds blow me yet'

**flybouy** · 03-03-2020, 10:00 AM

Quote:

Originally Posted by Pmedic4

Don't have a diesel, totally agree with the major difference being 'wind resistance'. With the Cougar hanging on, I get 8-9mpg generally. I also tow a UTV, which I haul on an aluminum trailer, which fully loaded is rated at 3,000 pounds. I was really surprised by the drop in mileage with this light trailer, and at best get 9-10mpg! It has a full length loading ramp, and I'm certain the wind hitting that ramp latched at 90 degrees is the culprit. I expected it to be more in the 12-14mpg range, but no it really drops off even with that trailer.

On a RV trip of 300 miles to Branson, I expected mileage to really suffer hitting the mountains in southern Missouri, but still hit about 8-9 on the way down. On the return, heading east out of Springfield MO, surprised to see I'm getting 11-12 and thinking I'm going to make it home on one fill-up. Then once I got heading north, now the onboard gauge is saying 6-7, and now thinking I have an engine problem. Of course, I stop for fuel, and the wind out of the north now is blowing 20mph, so I see the difference.

Wind definitely is the deciding factor, and so far I've not traveled 'Where the winds blow me yet'

Another often overlooked factor when traversing long distances is changes in elevation and grade.

Living on the east side of a "fall line" at or near sea level any drive west is a gain in elevation and a subsequent drop returning. Mountain ranges also have a "windward and a leeward sides" so one direction of travel will result in a steeper grade.

Just another factor like wind direction/intensity, traffic, driver inputs/variances etc. that effect m.p.g.

Spock123 · 03-05-2020, 04:11 AM

On my 2012 Silverado 3500 deleted diesel I was getting 12mpg or better pulling a Cedar Creek at 67mph. Came to Myrtle Beach on brand new Silverado 3500 getting 10mpg at 60mph. I have to find the sweet spot.

travelin texans · 02-24-2020, 08:20 AM

If towing 10k+ regularly in the mountains I'd recommend the the diesel for hp/torque + the engine brake.
Had an '05 & '13 Duramax duallies both got 8.5 to 11.5mpg towing 16.5k 5th wheels at usually 68mph (that was the sweet spot at 1700 rpm). The '13 had noticably more hp & torque, with the biggest difference in the 2 being the engine brake on the '13, set the engine brake, shift to tow/haul, set the cruise & let'er tow. Both averaged 17+/- empty at posted speed limits. As to the DEF usage, the '05 didn't require it & the '13 would hold a 2.5 gallon jug, half of a 5.3 gallon tank, every 3500 miles, towing didn't seem to affect usage. Wouldn't hesitate to buy another Duramax.

gearhead · 02-24-2020, 09:47 AM

It is what it is, but you could do a deep dive into aerodynamics to find the surface area vs. weight vs. wind speed. I'm thinking there is the factor of putting that resistance on a 11,000 pound truck vs. a 16,000 pound trailer, which I assume is why 18 wheelers have a "spoiler" on the truck to reduce the frontal effects on the much heavier trailer. Then there is the low pressure area behind the trailer that increases drag.
Get back to us when you get the factor of surface area of a low, mid, and full profile 5th.

gearhead · 02-24-2020, 09:58 AM

Or delve into downforce with a Chaparral race car history lesson and my cousin in law Andy Green:
https://driving.ca/chevrolet/auto-ne...ral-2x-concept

goducks · 02-24-2020, 11:58 AM

I towed 9200 lbs with a 2012 Ram CTD and loved it. More than enough power for any mtn pass. I live in Oregon so I see many hills and mtns during the camping season.
Effortless cruising on the freeway.
What I didn't like was the emission stuff. I now have a 2018 Ram 6.4 with 4.10 gears. Not near as nice for towing but still does the job. And $9200 cheaper.
Ironically the wife and I were looking at a 2800 mile trip down to Tucson. Just for giggles I figured what it would cost to take my 12 CTD vs my 18 6.4.
It was on $62 more to take the 6.4. Diesel prices are running .40-.50 more along the route and even with 8.5 mpg in the 6.4 vs 11 in the 12 CTD it's still a wash.
Do I miss my CTD? Heck yes. But I don't miss all the extras, like fuel filters, oil, DEF, possible WIF light, searching for quality diesel stations that I can fit in.

Ken / Claudia · 02-24-2020, 02:38 PM

What I always read in the gas v diesel is the upfront extra cost. Diesel is more than the gas engine trucks, BUT no one points out that the more upfront cost also carries more cost at resale time. Of course condition of any vehicle means more cash.

jsb5717 · 02-24-2020, 03:20 PM

I've never bought a new truck and don't plan to. It's a lot easier to get a good deal on a well-cared-for diesel so the upfront cost (gas vs diesel) isn't as much of an issue.

I've been pulling 5ers for about 30 years and after pulling with a gasser in the beginning I determined that I wouldn't be without a diesel. For me it's much less about economics (although I'm cheap by nature and look for my best deal), and mostly about the towing experience. There's just no comparison to me. The extra torque makes my experience a lot better and less stressful. The better fuel mileage is a nice perk and I get around 11 mpg towing and 18-20 otherwise.

Keystoned · 02-25-2020, 10:45 AM

There is a big hill north of me called La Bajada going towards Santa Fe. This is the test for me and I usually pass all the gassers while we are doing 60-65 towing. It is at about 6000 feet. Diesel for the win!

JimJan · 02-25-2020, 01:50 PM

We had a 6.0 gas 2500 Silverado and took out west with a bed camper, pulling a Jeep trailer. Fuel mileage averaged 10mpg. Picked up a 5th wheel and went to a Silverado 2500. Loved the power, Allison tranny and engine brake. Got 11.5 mpg average. Got a larger camper and a 3500 dually Silverado so we are back to averaging 10 mpg. Still love the added power and braking. No plan to go back as trade in value helps with a new one!

Frank G · 02-26-2020, 03:21 AM

Quote:

Originally Posted by ObiRich

I have a question or two. I've been toying with the idea of getting a newer truck to pull our 5er with. My current one is a 2009 Sliverado 1 ton, but it's a gasser. Although it does an adequate job pulling it, the fuel consumption is pretty high (get about 7-8mpg), and the engine revs pretty high when going up grades unless I really let the speed bleed off. We live in the mountains, so we do have a fair number of long grades. So I've been thinking about getting a diesel. But that's not the only reason I'm thinking of switching. My current truck is a long bed, and I'm just getting tired of the hassles when parking "the beast." Lastly, with a diesel, we could use the truck lanes when fueling if there's not an RV lane.

So my questions are directed more to Chevy or GMC diesel owners, as I'm looking at the Duramax. First what kind of mileage do you get when towing? Second, what kind of mileage do you get in day to day driving?

You will burn the lead out of 3 pencils trying to financially justify a diesel powered tow vehicle for recreational use. If you want one and can afford it, just do it and enjoy. Follow your own path.

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