# Mpg Worse Than I Expected?



## Eorb (Nov 5, 2008)

Hello everyone,
I just returned from my second trip with our new 21RS. What a great trailer, I smiled all weekend. After the first trip and the dismal gas mileage, I thought I would try and get some numbers on this trip. I have a 2007 Expedition EL, 2X4. Rated about 15-18 mpg on the highway. Here is what I got. On the way to Crooked River State Park (Ga), 180 miles, I had OD off, as the manual states. I drove about 65. I got a whopping 6.7 mpg. On the way home, I drove mostly with the OD on, only took it off when it might shift alot, like through city traffic, or numerous hills (overpasses in Fl). I was able to get 8.7 mpg. I drove 65 with OD, 60 when it was off. Is this dismal mpg normal? Thats only about half my non towing MPG. As far as Overdrive, I read the thread on it, and understand that the recommendation was turn it off when towing, but from what I could gather, the damage is because the higher gears cause to much shifting, which heats up the tranny. I figured if I was using OD, and it wasn't shifting, I was ok. 
I knew I would take a hit for pulling a aerodynamic brick, but its only about 5.5K lbs all loaded up. I am not going to trade to a diesal at this point, I am just wondering if anyone else experiences this low mpg. I might as well be driving a Class A! BTW, I checked the trailer wheels for heat to see the brakes were on, but they felt fine. Thanks.


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## Scoutr2 (Aug 21, 2006)

I average 9.2 mpg with my Chevy 2500HD, 6.0L, with the Outback in tow. But I only get about 13-14 mpg when not towing.Sounds likeyour engine is working mighty hard - probably the gear ratio causing the engine to struggle.

Just my guess.

Mike


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## 2500Ram (Oct 30, 2005)

Mileage sounds normal to me sorry it's not what your looking for, you are pulling a wind sail of a brick. 
Do watch out when towing in OD though. Do you have a locking converter for OD, if not your slipping the converter which is why the manual is telling you to drive in direct drive or I'll guess 3rd gear. If you have a locking converter than your fine until it starts shifting/hunting all the time between D and OD.

Good luck.


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## Collinsfam_WY (Nov 9, 2006)

Your mpg is very close to what we got with our '02 F150 SuperCrew with the same 5.4 engine. Well - you do have the 3V version which has a bit more "punch" to it and I think you have the 6spd trans vs. the old 4spd OD trans I had. Can you verify for me? With my older 2v 5.4 engine, I got about 6.5mpg towing our 23RS at 65mph with the OD off. I often felt like the engine and drivetrain was being pushed to its' absolute limits. The most memorable comment my DW ever said was once when we were pulling into a headwind, unable to go even 60mph. We were doing about 54mph with my foot nearly on the floor and engine bellowing at 4300-4400rpm with 18 wheelers overtaking us at 70+ on this small, no shoulder two lane farm to market road: After 20 minutes of pulling in these conditions, she lowered her shades, leaned back in the seat and without looking at me she said: "Wake me when the engine explodes, I am going to sleep".

See sig below for the solution to *all* of the problems mentioned above









-CC


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## Nathan (Jan 2, 2007)

Yes, unfortunately that sail behind you hurts the old fuel economy. I was getting ~7mpg with my F150 and the OB. The Diesel got me up to ~10mpg.









Now that was too good, so after one summer, we had to buy a trailer with more drag....








I'll tell you what I get after this summer's trip.


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## Oregon_Camper (Sep 13, 2004)

collinsfam_tx said:


> .... "Wake me when the engine explodes, I am going to sleep".


That is tooo funny. Surprised you didn't pull into the next dealers lot and solve the problem on the fly. You would of course have to wake her to move her to the new TV.


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## jasonrebecca (Oct 30, 2007)

That sounds about right.
On our trip to Yellowstone we averaged 10mpg over 2500 miles.
The worst I got was 8mpg going over steep mountain passes.
I only had the OD off when we were going up and down hills, mountains, etc. On the flats I had the OD on and cruised around 60-65 the entire trip. I am guessing you have the 3.55 gears in the Expedition. May want to go up to 3.73 since you are 2x4.


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## Eorb (Nov 5, 2008)

Thanks everyone, it sounds like what I am experiencing is about normal. I do have the 6 speed transmission, is changing the gears really an option, or are you talking replacing the vehicle.


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## PDX_Doug (Nov 16, 2004)

Eorb,

Your mileage sounds about right to me. Yeah, I know... OUCH! Just wait until gas goes back up over $4.00/Gallon!








Just to clarify though, the hit in your mileage has a lot more to do with aerodynamic drag than the weight you are pulling around. Drag increases with the square of speed. For example, if you go from 30MPH to 60MPH, you are doubling your speed, but quadrupling your drag. You have a lot of frontal area back there, and it adds up in a hurry.

What you will find is that you will reach a point where you will 'hit the wall' speed wise, and it will take an enormous increase in power (and reduction in MPG) to push through that. When I was pulling with my Titan, that wall was at about 62MPH. Below that, I could average about 10.0-10.5MPG, above that it dropped to 8.6 to 8.9MPG. And I'm talking about within about a 2MPH spread! Interestingly, I also found that once I got up to about 68MPH the mileage increased a bit again to about 9.2, but then fell off very sharply at about 72MPH. There was a definite sweet spot there, unfortunately it was at a higher speed than I normally feel safe when towing.

The moral of the story, is that the slower you can stand, the better your mileage will be. If you can keep it under 60, you will probably see a solid increase in milage, but still nowhere near what you get without the TT back there. Head and tail winds also contribute greatly to this equation, although I have found other weather conditions (rain), traffic, etc. seem to have less effect than one would expect.

Happy Trails,
Doug


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## Y-Guy (Jan 30, 2004)

Welcome to the world of bad MPG while towing! The weight, the drag, it all adds up fast. Slowing down will help some, the closer to 55 you run generally the more significant the gains in MPG will be. Try pushing 70 and see how low it can go!


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## mountainlady56 (Feb 13, 2006)

In reference to what Doug said, I used to try to keep my engine at 2K RPMs as much as possible. Of course, this isn't ALWAYS possible. I'm surprised with a 21RS with a 5.4L engine your gas mileage is that bad. BTW, I mainly kept my GMC Sierra 5.3 in OD during tow mode with no problem, whatsoever. When I put it OUT of OD, the RPMs seemed to rev more. I tried to find what I referred to as "the sweet spot" (the MPH where it would stay around 2K RPMs and not strain). Mine was usually (I DO remember THIS!







) 62 MPH.....so I just stayed in the slow lane and enjoyed the ride!!







I averaged 8.5 - 9 MPG.
Like others said, I eventually upgraded to a diesel, BUT, I was towing a 27RSDS, compared to your 21RS, which should be considerably heavier.
Good luck!
Doug, don't EVEN talk about gas going back to $4/gal!! I was finally able to take delivery of my Class C today........already had heart failure when I saw it had gone up to $1.89/gal (10 cent increase!).
Darlene


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## TurkeyBranch (Mar 12, 2009)

I am getting 9 mpg with my silverado 1500. I figure that is pretty good for pulling a 28 foot trailer. I only get 14 to 14.5 mpg without the trailer


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## Calvin&Hobbes (May 24, 2006)

We get about 11.5 w/o towing, 6.2 pulling the RQS. Of course we have the V-10, and the RQS is 8-9K. I call it the magic bus, because it makes gas disappear. Still, it's cheaper than a motel room, and I know who slept in the bed last night.


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## Carey (Mar 6, 2012)

About half of normal mpg is a good rule.. Even my dodge diesel gets around 10 towing. If I do 65 with a 6000 trailer I get maybe 11.. I might get 12 at 60 mph.. With any model 5er its always 10-11 mpg in perfect conditions.. Today in the wind I got around 8 at 62mph.. So just because its diesel doesnt mean its going to be that much better.. Yes I had a 8-9000lb 5er behind me, but even on a perfect day, I would feel lucky to get 10mpg..

Yep its much more about the drag from dynamics, rather than the drag from weight..

Is your Ex El broken in yet? It might do a tad better after that but not much more..

To think, you could have a 23-25 foot model and your mpg would be nearly the same..

Carey


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## MJRey (Jan 21, 2005)

When I used to tow with our old Expedition I would get anywhere from 8.5 to 11 mpg. I used OD if it would stay in 4th but with hills or wind I would have to turn off the OD. I usually drove about 60 to 62 mph and occasionally at 65 but the mileage dropped off quickly with the higher speed. I did have a Superchip custom tuner that helped with power and mpg but I did have to run premium fuel. Overall the improved mileage offset the higher price of fuel and the better power and shifting was worth it.


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## Oregon_Camper (Sep 13, 2004)

Calvin&Hobbes said:


> ...... and I know who slept in the bed last night.


Amen to that brother!!


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## Eorb (Nov 5, 2008)

Thanks everyone, I don't mind the mpg, just wanted to make sure I didn't have a problem.


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## compass49 (Feb 4, 2008)

Has anyone tried one of those roof mounted air deflectors? Would they actually help with the MPG or are they a waste money?


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## Rob_G (Feb 16, 2006)

PDX_Doug said:


> When I was pulling with my Titan, that wall was at about 62MPH. Below that, I could average about 10.0-10.5MPG, above that it dropped to 8.6 to 8.9MPG. And I'm talking about within about a 2MPH spread! Interestingly, I also found that once I got up to about 68MPH the mileage increased a bit again to about 9.2, but then fell off very sharply at about 72MPH. There was a definite sweet spot there, unfortunately it was at a higher speed than I normally feel safe when towing.


Wow... this is exactly what I was going to reply with... the sweet spots. Not sure what year that Titan was Doug, but with the new specs in the '08 I get between 11.0-11.5MPG... drops to 9.2-9.7MPG... then the top end in the mid 10's. Never gone over 74MPH with mine to find out any more.


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## tdvffjohn (Mar 10, 2005)

compass49 said:


> Has anyone tried one of those roof mounted air deflectors? Would they actually help with the MPG or are they a waste money?


I actually made a simple one when I had my Suburban out of wood and it sat in the luggage rack. It was a 96 with a 454. Fuel mileage increased maybe 1/2 mpg. The thing I noticed the most was that it actually towed easier with the wind deflected over the front. I had less sway when a truck or bus passed. The other major bonus was 75% less bugs on the front of the TT.

John


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## PDX_Doug (Nov 16, 2004)

compass49 said:


> Has anyone tried one of those roof mounted air deflectors? Would they actually help with the MPG or are they a waste money?


That's a good question. They do work, the question is how well and at what cost upfront. At first glance, I figured it probably wouldn't pay in the long run, but after running the numbers it may work for some. If we assume a price of about $300, fuel at $4.00/gallon an an increase in mileage of 1MPG (about 10% for most of us) it would take about 9,000 miles of towing to break even. That's quite a bit, although one cross country trip and back alone is going to account for the lions share of those miles.

Personally, we have done a total of about 6,000 miles over the last two years and that includes two big trips that we are not likely to duplicate anytime soon. Realistically for us, it would probably be at least a five year payback. And that's just breaking even

And this is all based on a lot of assumptions...

$300 for the wind deflector was a quick price I grabbed off E-Bay. I don't know if this was a good deal of not, or what quality of unit it was. If a more realistic price is $600, then double the mileage to payback.

$4.00/Gallon gas. We all saw this last summer, and it's likely we will see it again, but right now fuel is half that cost, therefore the savings are going to be half the example. Again, double the payback time.

Finally, how much saving can you really expect? I'm sure all the ads will make all kinds of wonderful claims, but what's realistic? I was always told that adding a canopy to my truck would smooth out the airflow over the trailer and I could expect a 1-1.5MPG increase in mileage. After having a canopy for a year now, my increase has been precisely... nothing! It's going to take awhile to recoup that $2,000 at this rate!









I have also noticed that a lot of people in this area that have these wind deflectors leave them installed and up all the time. I have to think that they are burning more fuel running around like that the 90% of the time they are not towing, than they are saving when they are towing!

So, I guess for some people (Carey!), it would be worthwhile. But for most of us it probably wouldn't be worth the effort or expense.


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## Nathan (Jan 2, 2007)

Rob_G said:


> When I was pulling with my Titan, that wall was at about 62MPH. Below that, I could average about 10.0-10.5MPG, above that it dropped to 8.6 to 8.9MPG. And I'm talking about within about a 2MPH spread! Interestingly, I also found that once I got up to about 68MPH the mileage increased a bit again to about 9.2, but then fell off very sharply at about 72MPH. There was a definite sweet spot there, unfortunately it was at a higher speed than I normally feel safe when towing.


Wow... this is exactly what I was going to reply with... the sweet spots. Not sure what year that Titan was Doug, but with the new specs in the '08 I get between 11.0-11.5MPG... drops to 9.2-9.7MPG... then the top end in the mid 10's. Never gone over 74MPH with mine to find out any more.
[/quote]
Everyone looking for sweet spots. Just remember that those tires on the OB are only rated for 65mph (unless you upgraded with a better aftermarket set).


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## GarethsDad (Apr 4, 2007)

The sweet spot on my f350 is at 1800 rpm or 63 mph. On our last trip out we averaged 16.5 mpg over the 700 mile trip. James


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## Frank's n beans (Aug 20, 2007)

Instead of spending money on the air deflector, I suggest an air intake and filter upgrade. I bought a K & N kit several years ago and got a 10% increase in fuel economy (11mpg to 12.5mpg). I get about 8.5mpg towing at 65 mph. It was about $250 and it gives me better milage every day.


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## Silvrsled (Jul 24, 2008)

I too was surprised at our mileage, but honestly, compared to some of you, I have nothing to complain about. When I got my diesel, I thought the mileage would be great, plenty of power, blah blah blah. So average on the freeway unloaded, I get about ~20mpg which is pretty good for 7500lbs flying down the road at 70+mph. When we tow our 21rs, I average about 12.8mpg. First time I towed this and got that mileage, I was shocked. Was expecting something more like 15mpg. Well, now i'm use to it so I guess I have to be happy with that mileage towing a brick. I enjoy diesel being cheaper than unleaded right now. Just paid $2.01/gal.


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## MJRey (Jan 21, 2005)

tdvffjohn said:


> Has anyone tried one of those roof mounted air deflectors? Would they actually help with the MPG or are they a waste money?


I actually made a simple one when I had my Suburban out of wood and it sat in the luggage rack. It was a 96 with a 454. Fuel mileage increased maybe 1/2 mpg. The thing I noticed the most was that it actually towed easier with the wind deflected over the front. I had less sway when a truck or bus passed. The other major bonus was 75% less bugs on the front of the TT.

John
[/quote]

The reduced sway or increased stability you noticed is interesting. With our Expedition I noticed a similar improvement in stability whenever I had the roof rack on the Expedition with the cargo box and bicycles. The extra stuff on the roof of the vehicle probably decreased the mileage but it wasn't enough to notice.


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## Rubrhammer (Nov 27, 2006)

Nowhere did I see any mention of what grade gasoline you are running. Todays modern ECMs constantly monitor for knock and make instantaneous adjustments to spark advance and fuel delivery. While more expensive to buy, premium or even 89 octane will allow your computor to feed more spark advance to the engine allowing a longer burn time for more power and economy. On those lines, a tune on your computor will expand the parameters that the ECM uses so that you can achieve even better results with better gas. My 27' trailer weighs 5500# ready to camp and with my Silverado with 3.73s on 89 octane I get over 11mpg average when towing.
Just another thing to look at.
Bob


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## hazmat456 (Jul 26, 2007)

I used top tow our 23krs with my mountaineer 5.0 with all wheel drive, over sized tires (31/10.5-15 up from LT235/75) and 3.73 gears. This thing gets 14mpg on the interstate, it's a brick itself. The outback weighs about 6k, I know overweight, but no sway or purposing and would stop in a hurry, I would get between 8-10mpg speed dependant 55-65. We switched to a dodge pick-up for the additional cargo room, 1/2 ton,5.9 magnum with 265000 on the clock(price was right) towing mileage did not change, empty I get about 16.


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## Dub (Dec 8, 2008)

Maybe try switching to a synthetic oil too? I have noticed a small increase in all of my vehicles when I switched them over to Mobil-1 full synthetic. I also run it for 7-10K miles too between changes and it comes out the same consistency that it goes in. Premium fuel would sometimes give me a small bump in mpg. The biggest thing you can do is drive 55mph. It will seem really slow at first, but even on an 8 hour trip you're only talking an extra hour of driving if you slow down. Me slowing down as a test last summer caused me to get a 2mpg increase. If I did it over the entire 3500 mile trip I would have saved almost $400 in fuel costs!


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## CamperFred (Mar 22, 2009)

Hey Dub,

What kind of mileage are you getting with your Tundra? I have a 08 Sequoia with the same powertrain and axle ratio as the Tundra. I get about 18-19mpg on hwy with 5 passengers and roof box. I wonder what kind of mileage drop I should expect with a trailer.

BTW I don't have an Outback. Still shopping for one...

-Fred



Dub said:


> Maybe try switching to a synthetic oil too? I have noticed a small increase in all of my vehicles when I switched them over to Mobil-1 full synthetic. I also run it for 7-10K miles too between changes and it comes out the same consistency that it goes in. Premium fuel would sometimes give me a small bump in mpg. The biggest thing you can do is drive 55mph. It will seem really slow at first, but even on an 8 hour trip you're only talking an extra hour of driving if you slow down. Me slowing down as a test last summer caused me to get a 2mpg increase. If I did it over the entire 3500 mile trip I would have saved almost $400 in fuel costs!


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## shake1969 (Sep 21, 2004)

I get about 7 or so with the rig in my sig.


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## Dub (Dec 8, 2008)

I get 18mpg on the highway fully loaded at 70mph, I get 19mpg if I slow down to 60-65mph. When towing I get anywhere between 9-11mpg. 9 with a headwind, 11 with a tailwind. Slowing down to 55mph will give me 1-2mpg more. Add premium and another small increase. Best I got was 13mpg using premium going 55mph on long section of the New York turnpike. And that's with 9500lbs behind me as i travel wet ;-)



CamperFred said:


> Hey Dub,
> 
> What kind of mileage are you getting with your Tundra? I have a 08 Sequoia with the same powertrain and axle ratio as the Tundra. I get about 18-19mpg on hwy with 5 passengers and roof box. I wonder what kind of mileage drop I should expect with a trailer.
> 
> ...


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## vikecowboy (Aug 17, 2006)

I wish I traveled at low altitude - but I get anywhere from 8-10 mpg pulling my 25rss with a 07 Tundra Crew Max.

I just got back from Phoenix - round trip through the mountains at Payson and Heber to Albuquerque, I averaged a little over 9 mpg. I usually go speed limit or slightly slower.


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## CamperFred (Mar 22, 2009)

Thanks for the info. I have an idea what mpg to expect.

-Fred



Dub said:


> Hey Dub,
> 
> What kind of mileage are you getting with your Tundra? I have a 08 Sequoia with the same powertrain and axle ratio as the Tundra. I get about 18-19mpg on hwy with 5 passengers and roof box. I wonder what kind of mileage drop I should expect with a trailer.
> 
> ...


[/quote]


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