3/4 ton fuel economy?

zuren

Adventurer
Assuming flat highway, no tailwind, truck is empty except for driver, modest A/T tires (eg. Cooper Discoverer AT), and cruise set at 60-65MPH, what kind of fuel mileage is everyone seeing?

I have a friend with a 2005 Dodge 2500, Cummins diesel, crew cab, manual tranny, who gets 24MPG if he is driving for economy. Mixed driving he claims around 19-20MPG. I'm not sure what gears he has. He is running a programmer so that may be helping. He is an engineer so I trust his observations and math.

Do these numbers seem fairly common and reproducible across 3/4 trucks? The best I can ever hope for is 20MPG out of my van; I averaged 19.8MPG last week driving across much of OH, PA, and NY.

Thanks!
 
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deserteagle56

Adventurer
My very first question would be - where are those figures coming from? Is he hand-calculating the mileage at every fillup, or just getting the figures from the overhead display?

Reason I ask is that EVERY vehicle I've owned has given very optimistic figures on the electronic display - most times by about 2 mpg.

I owned a 2004.5 Dodge/Cummins 2500 but with the automatic and 3.73 gears, otherwise totally stock including tires. Lifetime average (hand-calculated) was right at 18 mpg. I traded that truck for a 2004 Dodge/Cummins dually because I now pack around a cab-over camper but it has a 6 speed manual with 3.73 gears. Empty it also gets ~ 18 mpg and 14-15 mpg when packing the cabover and towing a trailer with a Jeep on it.

But then, I've never "driven for economy" figures. Nor do I romp on it or drag race it. That being said, driving conditions make all the difference in the world. If you spend a lot of time in stop-and-go traffic expect fuel economy to go down.

Just as a comparison, I also have an E-350 4x4 conversion with the V-10. Lifetime average - 12 mpg. Extremely dependable powertrain but it needs a larger fuel tank!
 
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zuren

Adventurer
My very first question would be - where are those figures coming from? Is he hand-calculating the mileage at every fillup, or just getting the figures from the overhead display?

He said they were his calculations based on manual calculations at fill-ups.
 

Dalko43

Explorer
There are a lot of different gearing and rear axle (DRW vs SRW) combinations out there so it's hard to get a consistent mpg average that is directly applicable to your own situation. And as deserteagle points out, a lot of people like to pretend (or they just don't know any better) that the mpg readout on the truck computer is accurate....usually that isn't the case and hand calculating is always the most accurate method. Also people sometimes upgrade tire sizes without adjusting the odometer readout. Just a lot of silly stuff like that which is why when you hear someone on an internet forum claim high fuel economy #'s, you should take it with a grain of salt.

I don't know whether that applies to your friend, but 24 mpg hwy for a common rail 5.9l Cummins does sound a bit on the high side...maybe it's doable if you really take it easy and milk the vehicle for every ounce of efficiency that is available. But for realistic hwy driving (accelerations, +70mph, uphills) I don't think it's a number you'll consistently see. TFL trucks did a mpg review for the new 6.7L cummins, where it got ~22mpg hwy even with all the emissions in place. However, the test was conducted on a short trip over mostly flat terrain...I'm not saying a 3/4 ton diesel can't get 22-24mpg hwy, but rather that under realistic driving conditions I'd expect at least 1-2 mpg lower.
 
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Roaddude

Long time off-grid vanlife adventurist
I have an '08 6.6 Duramax turbo-diesel, automatic, in an extended body Savana 2500 (with some 3500 parts added by Penske before my purchase) with 3.73, that I've driven for years and consistently get over 20mpg on the interstate, empty or mildly loaded. Around town for longer periods with lots of slow driving, traffic lights, and stop-n-go in traffic and it drops to an avg of 15 or so, sometimes lower. Consistent running at highway speeds for hours is when this van and engine are happiest.

Have been running it all stock, though with Michelin LTX M/S2 245/75R16 on stock rims. No cruise control, though I stay at a pretty steady speed on the Interstate. No 4x4, no lift, no trailer yet with this van, though that's all changing soon..

My previous van, a '98 6.5 Duramax in a one-ton was the same; happiest at highway speeds for long distances, though consistently got a mile or two less per gallon. I drove it 'til it had well over 500,000 miles and the engine was still going strong, but the body was getting hard.

I figure my mileage from tank to tank fill ups, mileage and gallons tracked to the tenth, and average over longer trips of three tankfuls or more. I typically go around 500 miles between tanks on longer trips, and then it usually drinks around 24gals. Then those trip averages are averaged over several trips. Mileage is sometimes a bit higher, depending on conditions and how much is highway as opposed to back roads and small towns, though I don't track weather and what the terrain has been. I think it would be impossible to figure flat highway, no tailwind, empty truck unless I have good flat terrain and a couple days to waste in perfectly calm weather going back and forth 'til I've used up couple tankfuls to get a decent average ;)

I've been disappointed lately in my mileage, but have been stuck in town for months with next to no long-distance highway miles, which is what both the van and I am used to the most.

I agree, at least in my case, that the on-board driver's info center as to current MPG and miles left figure is often optimistic, but has proven over time to be a fair gauge while driving. Haven't run out of fuel yet in this van, and only once or twice have fueled up and had to put in more than 26gals of the stated 31 gal capacity.

I just got the BlueDriver bluetooth deal you plug into the OBDII port and read on your iPhone, and am interested in what info it provides and how accurate it may be.
 
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Martinjmpr

Wiffleball Batter
My very first question would be - where are those figures coming from? Is he hand-calculating the mileage at every fillup, or just getting the figures from the overhead display?
.
Reason I ask is that EVERY vehicle I've owned has given very optimistic figures on the electronic display - most times by about 2 mpg.
.
I observed the same thing until I got my Suburban. The Drivers Information Center (DIC) has an MPG display and mine has been surprisingly accurate - in fact, it's been much more accurate and reliable than my Scangauge II, even though I've calibrated the SG, the DIC MPG display is always more accurate, to within a couple tenths of an MPG per fill up (based on my hand calculations.)
 

Comanche Scott

Expedition Leader
From the short time I've had an '07 Dodge Ram 2500, it appears to me the fuel mileage display is based on either a period of driving time, or miles (or maybe both).
I don't think that period of miles or time is too much (maybe half hour/30 miles, but that is just a guess).

On the flats of Oregon, and California, it stayed pretty steady. On the long climb through the mountains in Washington, Oregon, and Northern California, it would read high when coming down long grades, and low when climbing long grades.

It does not seem to track the whole tank, but there are certain points during the trip it was very close. Other parts of the trip it was almost 3mpg off actual hand calculated.
I seem to remember this being similar to how my '04 Grand Cherokee display functioned.
 

Roaddude

Long time off-grid vanlife adventurist
.
I observed the same thing until I got my Suburban. The Drivers Information Center (DIC) has an MPG display and mine has been surprisingly accurate - in fact, it's been much more accurate and reliable than my Scangauge II, even though I've calibrated the SG, the DIC MPG display is always more accurate, to within a couple tenths of an MPG per fill up (based on my hand calculations.)

From the short time I've had an '07 Dodge Ram 2500, it appears to me the fuel mileage display is based on either a period of driving time, or miles (or maybe both).
I don't think that period of miles or time is too much (maybe half hour/30 miles, but that is just a guess).

On the flats of Oregon, and California, it stayed pretty steady. On the long climb through the mountains in Washington, Oregon, and Northern California, it would read high when coming down long grades, and low when climbing long grades.

It does not seem to track the whole tank, but there are certain points during the trip it was very close. Other parts of the trip it was almost 3mpg off actual hand calculated.
I seem to remember this being similar to how my '04 Grand Cherokee display functioned.

Interesting, and I wonder if the DICs for GM and Dodge base calcs on different criteria. I know mine (GM) acts quite logically, varying in projected mpg and miles remaining depending on how hard the engine is working, I assume. Semi-coasting downhill or decent tailwind or drafting a ways behind a big rig trailer all seem to make it vary, then it evens back out when simply cruising. I never really count on it much unless at highway speed, as the miles remaining figure seems to jump all over when parked a lot. Also have noticed that miles remaining drops considerably if parked with the nose up, and is much higher upon startup if parked with the rear end higher. Then it levels out, too, after a few miles and a couple corners. Which leads me to believe it is reading the actual tank level itself and then adding in speed and miles already driven to come up with a number for both mpg and potential miles remaining in a tank. I often zero the mpg when hitting thr highway on a longer trip and watch it climb to crazy levels. I have pics of my DIC saying like 28mpg. Then it levels out after a bit of steady driving to the more normal 20-22.

Will also be interesting to see how figures compare with the bluetooth BlueDriver (similar in op to the ScanGauge). I always thought these gauges must be far more accurate, so interesting to see your experience has been different.

I have a Maine to El Paso and back trip coming up beginning next week that will give me plenty opportunity to track it all. About half the trip with no trailer and less load in the van, other half with trailer and more loaded.
 
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Comanche Scott

Expedition Leader
When in doubt, read the manual.

This is a pretty cool thread! Made me go back and read the Owner's Manual. :)

Here is what is says in the Owners Manual of this '07 Dodge.
Based on this, I think either my previous post is wrong, or I'm not understanding the manual correctly.
Most likely I was just wrong... lol
 

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D45

Explorer
My old truck, a 2004 Dodge Ram 3500 Quad Cab, 4x4, long bed, diesel was able to get anywhere from 16-19

This depended on the programmer's tune level I ran at the time and the time of year (fuels)

Keep in mind, this was with a 6" lift, 37s and 4.10 gears
 

NatersXJ6

Explorer
2005 F250 6.0 Powerstroke. 5 Speed Auto and 4.30 gears. 4x4, totally stock, factory tires, no lift, no tuners or exhaust or deletes or anything else. Moderate to mildly aggressive driving, they are California streets I'm on.

I've been hand calculating it off and on for years and have seen a range from 16.5 to 17.5, with no significant swings either way. I checked it again today after running about 400 miles and it was 16.95. I think I'm done checking now.
It is consistent.
 

twodollars

Active member
My current 1994 k2500 burb with a 6.5 p400 is pretry consistent at 17mpg with me running at 75 to 80. If I slow down to 60 to 65 the number go's up to 19 to 20. 3.73 gears, 285 tires.
 

dmoo

New member
I recently got into a diesel truck from a 6.0 gas (which got terrible gas mileage). My "new" to me truck is a 2002 2500HD, 6.6 duramax with 90k miles. I am pleasantly surprised with the fuel mileage, I have been averaging 20-23 MPG unloaded at 60-70 mph highway driving, high teen mpg in town driving.

I tow cars intermittently and haul firewood, which is the real reason for the truck, but now I'm considering trying to take it on a trip/mild off road and see how it does. Diesel in my area is usually 12-20 cents more than regular unleaded. And my jeep grand Cherokee with the lift and tires is only getting 16 MPG....
 

Roaddude

Long time off-grid vanlife adventurist
I recently got into a diesel truck from a 6.0 gas (which got terrible gas mileage). My "new" to me truck is a 2002 2500HD, 6.6 duramax with 90k miles. I am pleasantly surprised with the fuel mileage, I have been averaging 20-23 MPG unloaded at 60-70 mph highway driving, high teen mpg in town driving.

I tow cars intermittently and haul firewood, which is the real reason for the truck, but now I'm considering trying to take it on a trip/mild off road and see how it does. Diesel in my area is usually 12-20 cents more than regular unleaded. And my jeep grand Cherokee with the lift and tires is only getting 16 MPG....

Yeah, cool, great to see another 6.6 Duramax owner with similar results. Same experience with my previous van, too, which was a '98 6.5 Duramax. As for getting off the pavement, I've had both my Duramax's off-road, though never on highly technical trails or rock-crawling. Plenty of "4wd or high-clearance only" type roads in the SW desert lands, though, always without problem. I've never had a problem with rwd only in these vans in severe winter conditions, either. That said, though, I'm itching to get a 4x4 conversion so I can go further back-country and do a lot more off-grid with greater peace of mind. Picking up a new XV-2 trailer this week to tow behind and use as base camp, too, and having 4x4 will allow me to haul it further back-country.

Diesel prices: yeah, depending on where and when, diesel is usually more expensive these days, though every once in awhile I see it priced below reg gas. The Gas Buddy App is really helpful in that regard, especially when traveling. I've seen differences of .15 and more per gallon within ten miles of each other. A lot of times all it means is doing the business bypass through a small town instead of hitting the station at the state highway or Interstate. Most of the small towns across America are a lot more interesting, too, with great cafés and diners and other small retail.

When I first started driving diesels in personal vehicles, diesel would always fluctuate a lot more than gas prices, but was always way less. My understanding is the govt or oil companies got involved in the early 2000's because truckers and the rail system were throwing fits at the constantly changing prices, making it hard for them to bid jobs accurately or forecast their potential earnings for a given quarter. They said, essentially, "you want a more consistent price, okay, here!" and set the prices a lot higher to cover their own butts, and it's been higher ever since.
 

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