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2500hd duramax towing mpg

MikeZ65
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MikeZ65 Enthusiast

MikeZ65

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Hello. 
I have a 2020 2500hd duramax with 16000 miles. On highway not towing I can get between 19-21 mpg.  But when towing our travel trailer which weighs about 9000# the very best I have ever got on highway is 10.2.  Does this sound right?  A guy with same truck at campground says he gets about 13 mpg and he’s pulling a 5th wheel. 
 

thx for any help

Edited by MikeZ65
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Random Enthusiast

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57 minutes ago, MikeZ65 said:

Hello. 
I have a 2020 2500hd duramax with 16000 miles. On highway not towing I can get between 19-21 mpg.  But when towing our travel trailer which weighs about 9000# the very best I have ever got on highway is 10.2.  Does this sound right?  A guy with same truck at campground says he gets about 13 mpg and he’s pulling a 5th wheel. 
 

thx for any help

Speed is the killer of MPG when towing. I've found that if I don't try keeping up with traffic I average 12-14 mpg on the highway towing my travel trailer of about the same weight. The worst mileage I've had was towing through the mountains and that was still 10-11 mpg. If you are relying upon your truck's display for MPG average, you might try hand calculating to see if it's just too far off. Something else to consider is how you have your rig setup. The travel trailer should set level as possible while towing. Check tire pressures on truck and trailer, low pressure can lead to poor MPG. Tire or suspension modifications definitely, such as a lift/level can set you back too. I remember replacing my truck tires with a lot more aggressive tread and I dropped about 1 MPG.

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MikeZ65 Enthusiast

MikeZ65

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Thanks. Most I will do is speed limit but more times than not I am 5 or so below. Stock ltz no mods. I do sometimes wonder if it ever finds final gear. Is there a way to tell what gear the truck is in while going down road.  10mpg just seems low for flat Florida    Thx again

unit Enthusiast

unit

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Posted (edited)

I've towed my 30' Airstream to the west coast and back from Ohio, 6,500 miles total, and averaged 13.4 mpg.  That's legitimate hand calculated mileage.  The trailer weights about 8,400 lbs loaded.  I have a Banks iDash and it displays the active gear, which is the only way I know with a GMC or Sierra to tell the gear.  It seems counter intuitive but I find I get the best mileage when the truck is in 10th gear.  At 60 or 62 in tow/haul mode the truck stays in 9th gear most of the time.  If I speed up to 68 or 69 the truck will shift to 10th and mileage goes up a smidge.  Normally, I would swear that you'd always get better mileage at a lower speed but this truck is different than others I've had.  I can only attribute it to the 10 speed transmission with it's three overdrive gears.  Fords and Rams will display the trans gear on the dash - not sure why GM doesn't.  It's really nice to know what gear the truck is in at any given time.

 

This is my experience and others will have different results.  Wind speed, wind direction, altitude as well as the weather are also factors that can affect mileage in different ways.  Size, weight and shape of the trailer also play a huge part in fuel mileage.

Edited by unit
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Michael621 Enthusiast

Michael621

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Posted

My first tow with a 5er of similar weight last month was over a mountain pass in WA.  Got 12 MPG on the trip (hand calculated). Speed limit was 70 a lot of the way, but kept the cruise at 5 over the posted truck speed of 60. Got passed left and right, but did not care. With the price of diesel what it is, no big hurry! I get what you do without towing, got 4k on the clock.

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MikeZ65 Enthusiast

MikeZ65

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25 minutes ago, unit said:

I've towed my 30' Airstream to the west coast and back from Ohio, 6,500 miles total, and averaged 13.4 mpg.  That's legitimate hand calculated mileage.  The trailer weights about 8,400 lbs loaded.  I have a Banks iDash and it displays the active gear, which is the only way I know with a GMC or Sierra to tell the gear.  It seems counter intuitive but I find I get the best mileage when the truck is in 10th gear.  At 60 or 62 in tow/haul mode the truck stays in 9th gear most of the time.  If I speed up to 68 or 69 the truck will shift to 10th and mileage goes up a smidge.  Normally, I would swear that you'd always get better mileage at a lower speed but this truck is different than others I've had.  I can only attribute it to the 10 speed transmission with it's three overdrive gears.  Fords and Rams will display the trans gear on the dash - not sure why GM doesn't.  It's really nice to know what gear the truck is in at any given time.

 

This is my experience and others will have different results.  Wind speed, wind direction, altitude as well as the weather are also factors that can affect mileage in different ways.  Size, weight and shape of the trailer also play a huge part in fuel mileage.

 

25 minutes ago, unit said:

I've towed my 30' Airstream to the west coast and back from Ohio, 6,500 miles total, and averaged 13.4 mpg.  That's legitimate hand calculated mileage.  The trailer weights about 8,400 lbs loaded.  I have a Banks iDash and it displays the active gear, which is the only way I know with a GMC or Sierra to tell the gear.  It seems counter intuitive but I find I get the best mileage when the truck is in 10th gear.  At 60 or 62 in tow/haul mode the truck stays in 9th gear most of the time.  If I speed up to 68 or 69 the truck will shift to 10th and mileage goes up a smidge.  Normally, I would swear that you'd always get better mileage at a lower speed but this truck is different than others I've had.  I can only attribute it to the 10 speed transmission with it's three overdrive gears.  Fords and Rams will display the trans gear on the dash - not sure why GM doesn't.  It's really nice to know what gear the truck is in at any given time.

 

This is my experience and others will have different results.  Wind speed, wind direction, altitude as well as the weather are also factors that can affect mileage in different ways.  Size, weight and shape of the trailer also play a huge part in fuel mileage.

I need to look into the banks idash.  I really would like to know what gear it is in. As mentioned with price of diesel I need every mpg I can get. 

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shadow gray 2020 hd Enthusiast

shadow gray 2020 hd

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Posted

Average seems to be about 13 mpg for me when in tow haul mode no matter what I am pulling.  I have not really loaded it down heavy, heaviest loads I have had on the truck has been my 22ft equipment trailer and 4 large bales of hay, probably somewhere between 9,000-10,000 lbs loaded trailer.  I get average about 18 mpg with mixed driving.  Those figures are from the trucks computer, I have not hand calculated.  

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Sumrtime Enthusiast

Sumrtime

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Posted

I have a 21 GMC Denali 3500 Long bed SRW. Truck has just over 15K miles. I tow a 42" 5th wheel that weighs right at 14K. Granted I have yet to tow any real distance (most trips were 1 hour or less) my average towing is 8.5. 

KC Desert Enthusiast

KC Desert

Posted
Posted

With a lot of headwinds out West I tend to get only 5-7 MPG if I am lucky. It’s sucks having only a 36 gallon tank. In perfect, level conditions I might get 10 MPG with my 36’ 5th wheel. 

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