Fuel Mileage while Towing

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jwynnejr1

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What kind of fuel mileage are y'all seeing while towing?

I pulled a 4,000 lb load last week 175 miles and burned a half tank (around 15 gallons) of diesel. 11/12 miles per gallon with that light of a load is bothersome. Haven't pulled a goose neck or fifth wheel far enough to measure fuel mileage yet, but I'm afraid it is going to be very poor.
 

PH Tanker

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I pulled my 37.5' travel trailer 8743lb from California to Texas averaging 9-10mpg at 70-75mph....
 
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jwynnejr1

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I pulled my 37.5' travel trailer 8743lb from California to Texas averaging 9-10mpg at 70-75mph....

Did you calculate it or use the mpg the dash showed? I've found that the average MPG on the dash (on my truck at least) is off by a couple miles.
 

sandawilliams

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Did you calculate it or use the mpg the dash showed? I've found that the average MPG on the dash (on my truck at least) is off by a couple miles.

Yep- the evic is a feel good gauge. Hand calculate and it may bring a tear to your eye. Mine is off by 2 mpg most of the time.
 
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Jaywoo

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Yep- the evic is a feel good gauge. Hand calculate and it may bring a tear to your eye. Mine is off by 2 gpm most of the time.

2 gallons per mile? Geez! That’s some horrible mileage. Lol!
 

chri5k

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The other thing to consider is frontal area of the trailer. It has as much or more of an effect on mileage than weight. A relatively light trailer with a large frontal area will put more drag on the tow vehicle resulting in reduced fuel economy. I pull a 13000 Lb horse trailer and get around 10 MPG (hand calculated) at around 65 MPH. If I increase speed to 75, my milage drops to around 7.5 MPG.
 

Elkman

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My truck averages between 9 and 13 mpg depending on how fast I am driving and whether there is a head wind. A 10 mph headwind makes the air drag at 65 mph the same as driving at 75 mph and no wind. Air drag increases with the square of your effective speed (truck speed and wind speed) so 4x as much air drag at 70 mph as compared to 35 mph. A cross wind exerts 2/3 the vector force of a headwind to a 15 mph crosswind is like pushing through a 10 mph headwind.

Still my trucks diesel 13 mpg would be 8-9 mpg with a gas V-8 engine and I care less about the cost of the fuel as I pay $1.00 more for diesel than for regular gas, but I get 30% more miles on a tank of gas and when towing that is a blessing with fewer fuel stops.

I periodically add a combination cetane booster and fuel injector cleaner to the tank. Having a better spray pattern can't hurt and cost of the additive is low at about $6 per use.
 
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jwynnejr1

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The other thing to consider is frontal area of the trailer. It has as much or more of an effect on mileage than weight. A relatively light trailer with a large frontal area will put more drag on the tow vehicle resulting in reduced fuel economy. I pull a 13000 Lb horse trailer and get around 10 MPG (hand calculated) at around 65 MPH. If I increase speed to 75, my milage drops to around 7.5 MPG.

Very valid. I was pulling a flat front enclosed trailer


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jwynnejr1

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My truck averages between 9 and 13 mpg depending on how fast I am driving and whether there is a head wind. A 10 mph headwind makes the air drag at 65 mph the same as driving at 75 mph and no wind. Air drag increases with the square of your effective speed (truck speed and wind speed) so 4x as much air drag at 70 mph as compared to 35 mph. A cross wind exerts 2/3 the vector force of a headwind to a 15 mph crosswind is like pushing through a 10 mph headwind.

Still my trucks diesel 13 mpg would be 8-9 mpg with a gas V-8 engine and I care less about the cost of the fuel as I pay $1.00 more for diesel than for regular gas, but I get 30% more miles on a tank of gas and when towing that is a blessing with fewer fuel stops.

I periodically add a combination cetane booster and fuel injector cleaner to the tank. Having a better spray pattern can't hurt and cost of the additive is low at about $6 per use.

Damnit there’s always an engineer in the crowd.


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SouthTexan

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My towing mileage mainly depends on five things which are generally not always constant. Speed, aerodynamics of what I am towing, the direction/speed of the wind, road grade, and the one with the least impact is weight. I have towed the same trailer at the same speed with and without a heavy headwind and gotten up to a 2 mpg difference. There was also a 1-2 mpg difference when towing my RV 65 mph instead of 70 mph 160 miles down to the coast with the same wind.

Weight really does not have that much of an impact until you start getting really heavy. I bet I would probably get better fuel mileage towing a flatbed bumper pull trailer with little aerodynamic drag with 12k on it than I would towing a 6k bumper pull RV with a lot of drag.
 

chri5k

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Weight mainly affects rolling resistance. Bigger contact patch from the flatter tire, etc. Also more tires usually means more rolling resistance. There was a graphic somewhere showing the components of drag that illustrated the effects of rolling resistance. For most of our towing applications wind resistance is the much bigger component. Rolling resistance comes more into play with 18 wheelers.
 
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jwynnejr1

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Okay guys...I
Understand forces across surface
areas and air resistance. I was wondering how y’all were doing on fuel efficiency while towing


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SouthTexan

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As I stated in my post, it all depends on the conditions for my mileage. I tow my 13k RV 160 miles down to the coast every year down the same roads. Sometimes I will get 9 mpg and sometimes I will get 12 mpg both at same speeds. All based on calculated numbers, not EVIC.

I will point out that even unloaded and in other vehicles I generally get horrible fuel mileage on this route which I take at least 10 times a year. Half the route is nothing but farm land on both sides and there are no trees to block the wind. My average fuel mileage starts to drop once I hit this section in all my vehicles. I can take my RV somewhere else like 100 miles north to Marble Falls and get 1-2 mpg better because there are trees blocking most of the wind on both sides.
 

NH RAM

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OOP's but that is what I tell tree huggers when they ask about my mpg on that 'BIG f'ing truck'.
These are the same people I see stuck in the winter as I drive by with my "gas hog" and 1000# V-plow. I know I should help, but to save the environment, I keep driving so I don't burn any extra fuel ;)
 

G. Mcpherson

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I have been avg. about 13 mpg. 29 ft. Travel Trailer at about 8k.
 

stembridge

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I've been pulling a 24' enclosed trailer (10K rated) as we've moved from the Middle West to a more liberty-respecting State in the South. Weather and wind had a significant impact on fuel economy. On a nice day with light winds, I've averaged around 7-8 MPG loaded and maybe 9-10 empty. Bucking a headwind, that drops to 6-7 MPG, and my worst tank was about 5.9. The truck itself (no load, no trailer) normally gets around 13-15 MPG.

2020_ram-24ft-trailer.jpg

I have no idea what the trailer itself weighs, but I'd bet some of my loads have had me at the limit of my truck's rating. The 5.7 has power enough (for me), but the stupid transmission programming (even in tow mode) is incompetent at best. I saw a *lot* of this pulling into the wind:

2020_ram-mpg.jpg

es
 

62Blazer

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The other thing to consider is frontal area of the trailer. It has as much or more of an effect on mileage than weight. A relatively light trailer with a large frontal area will put more drag on the tow vehicle resulting in reduced fuel economy. I pull a 13000 Lb horse trailer and get around 10 MPG (hand calculated) at around 65 MPH. If I increase speed to 75, my milage drops to around 7.5 MPG.
The frontal area that causes wind resistance is one thing a lot of people don't take into consideration. Had a friend that was excited because his new trailer was 1,500 lbs. lighter and was thinking it would pull easier....however he didn't take into account that it was 12" taller and if going faster than 60 mph it pulls harder than his last trailer. It's also just not the frontal area of the trailer that causes wind drag. As said in an above post even a 100% side wind will cause a lot of drag.

Another good point about wind resistance was also mentioned in that post also regarding how it increases by an exponential amount with speed. For example if you look at 60 mph vs. 70 mph. 60^2 (squared) is 3,600 where as 70^2 is 4,900. That basically means increasing your speed on the freeway by less than 17% causes an increase in wind resistance/aerodynamic drag of over 36%.
 

Gr8bawana

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My towing mpg is anywhere from 13-16mpg with my TT of about 8500lbs. I set the cruise control at 65mph and enjoy the scenery.
Truck has 3.42 gears and stock size 275/70/18 tires.
 

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