7mpg!?

Totally new to RV'ing and just got back from our first trip with our "new to us" travel trailer.  I knew the mpg were going to drop off like a brick but I never expected 7mpg...  and I mean the bottom end of 7, not 7.8 or 7.9.  I'm talking 7.0.  So I have a few question.

First of all I'm towing with a 2011 Tacoma double cab 4x4 V6 long bed, tow package, weight distributing hitch and a fiberglass camper shell.  The TT is 19ft and weighs 4500lbs loaded. I aired up all the tires to 37psi.  The entire trip trip was on flat ground with no wind and I stayed in 4 as opposed to D.  Stayed around 60mph the whole way and never above 65.

Is this normal?  I was expecting to get around 10-11 with this setup.  I mean 7 just seems a bit low.. I was planning on taking it up in the mountains eventually but I can't imagine what it would be going uphill with a headwind.  5 maybe!?  I thought the consensus was never tow in overdrive but talking to some other guys who tow they were saying with newer trucks its ok to tow in D and let the tranny do its thing as long as its not hunting.  What do you guys think about towing in D?  Any other tips on maximizing gas mileage.  Don't think I'll be going more than 55 on the next trip. 

Also, I can't help but think that I'm destroying my truck when I'm only getting 7mpg.  Could someone please reassure me that I'm not going to trash my trucks engine towing in this config?  :-\ Thanks!

kalaniwavo said:

Totally new to RV'ing and just got back from our first trip with our "new to us" travel trailer.  I knew the mpg were going to drop off like a brick but I never expected 7mpg...  and I mean the bottom end of 7, not 7.8 or 7.9.  I'm talking 7.0.  So I have a few question.

First of all I'm towing with a 2011 Tacoma double cab 4x4 V6 long bed, tow package, weight distributing hitch and a fiberglass camper shell.  The TT is 19ft and weighs 4500lbs loaded. I aired up all the tires to 37psi. What is the max tire pressure on the tires sidewalls.  37 seems awfully low. The entire trip trip was on flat ground with no wind and I stayed in 4 as opposed to D.  Stayed around 60mph the whole way and never above 65.Anything above 55 and you are going to see a drop in economy.

Is this normal?  I was expecting to get around 10-11 with this setup.  I mean 7 just seems a bit low.. I was planning on taking it up in the mountains eventually but I can't imagine what it would be going uphill with a headwind.  5 maybe!?  I thought the consensus was never tow in overdrive but talking to some other guys who tow they were saying with newer trucks its ok to tow in D and let the tranny do its thing as long as its not hunting.  What do you guys think about towing in D?  Any other tips on maximizing gas mileage.  Don't think I'll be going more than 55 on the next trip. 

Also, I can't help but think that I'm destroying my truck when I'm only getting 7mpg.  Could someone please reassure me that I'm not going to trash my trucks engine towing in this config?  :-\ Thanks!

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I suspect since you have a double cab that you have more than two people in the truck?  Have you actually weighed the  loaded ready to camp combination?  I'm going to go out on a limb here and say you are probably way overloaded.

Not that familiar with the Tacoma tranny, but with my 08 Dodge Dakota the trans has a tow/haul mode I select when towing. My Dakota has the 4.7 Magnum V -8 and has 3.92:1 gears. I tow a Rockwood ultra light that weight about 6300 loaded per CAT scale. My millage avg is between 8 and 9 mpg depending on wind. I leave the trans in "D" and let the tow/haul mode take care of the shifting on hills. I usually tow at about 65 or as close to as possible. In your case I think it's the V-6 that's the issue, just not enough torque/horsepower. I've know several other people that gave up on their V-6's when hauling even lighter trls then yours.

Sounds about right, my Xterra used to do the same with a similar weight trailer.  Slow down to 55 and you'll see a slight improvement.  It's not as much the weight as the large white box behind.

Its obvious that this V6 is working HARD,, as such you can't expect very good mileage,, those little engines are for mileage not for work and they don't produce torque at a low RPM where mileage is good.>>>Dan

seems really low... pull into a truck stop and weigh the entire rig.  According to your numbers, the total should be about 10,000lb or less...maybe 9000.  Sounds like it is closer to 12,000.  Check to verify that the trailer wheels are spinning freely and inflated to hiway pressure too.  What mpg do you get in the truck, loaded, w/o the trailer?

Guys I wprked around on construction sites never bragged about the Tacoma gas mileage..it's heart and longevity  and the well built feeling...but most said they got 12 to 15 on the hgwy..
If it makes you feel amy better my Elandan gets 5 mpg and my DP gets about 8mpg. It is what it is.

Just 2 people in the truck and our 1mo. old so an extra 10lbs there.    but other than the camper shell (200lbs max) thats it for payload.  I included gear in the bed of the truck in the total of 4500lbs.  the hitch maybe an extra 100bs... but with a max tow rating of 6500lbs I thought 4500lbs would be ok.  obviously less would be better, but I figured 2/3rds of the max capacity shouldn't be that bad and definitely not into the overloaded category.  a new truck isn't an option so its either live with it or part ways with the trailer.... 

freeway unloaded 18mpg.  checked the tire pressure before and after and was at 37psi all around.  I'll roll thru a weigh station with everything and see what I get.  got the taco for the reliability too but if its going to blow at 100k because its overloaded I might rethink the trailer

max pressure stamepd on the side of the trailer tires says 35 which seemes really low to me as well..  think they are light load tires?  I didn't look that hard

35 psi was the same on my old trailer.

It's likely the wall you drag in the wind more than the weight.  Try a flat bed trailer with steel plates to the same weight and it will be much easier to tow.

Slow down to 55 on your next trip to compare.

in really rough terms, 18mpg/7mpg is a factor of 2.6; 2.6 times as much energy towing as not towing.  On level hiway, no head wind, the extra load is due to wheel rolling drag and aerodynamic drag.  The trailer adds a lot of square ft to the profile, but it would have to add at least twice the front area as a bare truck  to result in this mpg.  The other big factor, someone else mentioned, is if the engine is forced to run at high RPM to create enough torque to move the rig at 65.  High RPM gobbles gas.  You can try running without the trailer at the same gear/rpm and see if the mpg goes way down...?

Your remaining option is, as you noted, to slow to 55mph... drag is proportional to speed squared so while 65 is 18% faster, it is about 40% more drag.  RVs and trailers are not low drag...

Hope you make it work.

All good advice above. That V6 is working hard to produce enough Hp & torque to move that big front wall through the air, and poor fuel economy is the price you pay for it.  In this case, a "big block" engine would perform better, simply because it is able to produce the required hp at a lower rpm and thus less fuel.

If you tow more than you drive empty, a more powerful truck would be a good choice, but if towing is only an occasional thing, suck it up and pay the price when you tow. And SLOW DOWN - wind resistance increases with the square of the speed, so even dropping from 60 to 55 has a big effect. You may even be able to run in OD where it is level, and that higher gear may help too. Experiment and see.

We too learned that one the hard way, we tried pulling a 3500 lb fiver with a V-6 Ranger. We couldn't pass a fat kid on a bicycle on the hills and fuel consumption was horrible.
As the others have said, you are expecting too much from that poor truck. You either need to upgrade to a full size truck with a V-8 or live with the misery.

Hi,
Another vote for "not enough power" and perhaps more like 70 than 65? For your information, the drag of the trailer will DOUBLE if speed increases from 55 to 70 MPH! Given the flat plate front of the trailer, it is entirely possible that overall drag is increased by a factor of three (the truck is at least somewhat streamlined), let alone two.
Just FYI,
Ernie

the other option is to ditch that trailer for a hi-lo of some kind. it will help out greatly.

RoyM said:

We couldn't pass a fat kid on a bicycle on the hills.

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LMAO.....

I will have to agree with the majority, The truck and engine are way too small. Those trucks were made to be used as passenger vehicles. It will not tow any trailer satisfactory. Dont try to fix it as you will spend a lot of money without much improvement.
Sorry!!

I tend to agree with the group the engine is just too small for your load. You have to consider the HP/TQ rating of that engine... Gasoline engines tend to produce there highest amount of TQ at high RPM's which is just inefficent for MPG's. So the only way you going to over come this problem is with a larger engine (more cubes of displacement) or like Gary said just suck it up and pay the bill.

Not only do you have to consider you weight factor of the tow vehicle but also consider the power plant ability to haul said weight.

I would like to answer this question in a general way from my own exprience with trucks over 60+ years.

Light trucks, with little engines have never been efficient for work such as towing. As truckers can tell you, the way to get the best fuel mileage is to use larger engines running at lower RPM's. This is oposite to what is commonly heard by those who would like all of use to buy and use smaller vehicles.

One reason that Diesel engines are more and more popular is that they run at lower RPMs than Gas engines to produce the torque. There are also other reasons also but consider, everytime that piston in the engine compresses the fuel at 3,000 RPM it is using more fuel than compressing at 2,000 RPM.

To give an example from our own records, years ago, with cheap fuel our semi trucks were equiped with 290 to 350 HP Diesels. We averaged close to 4 or 5 MPG with those. When fuel skyrocked in price we went to what we use now, 550 to 600 HP engines and get 12 to 14 MPG with heavier truck loads and larger trucks and trailers.

I am a rancher and truck company owner. I also have a Montana 5th wheel 3750FL that is one of the larger RV trailers. Using any of our Dodge D3500 Diesels, with the higher power Commins Engines, with 5 or 6 Speed Manual Tranmissions, I average around 16 MPG pulling our 39 Ft Montana.

I believe from our experience on the Ranches' trucks, tractors, and with our commercial trucks, that too many times people try to get buy with pulling vehicles that are too small and too light and weak for the job. You will never be sorry that you have too much power.

I used to tow with a Suburban 5.7 gas V8, w/o a trailer I averaged 17 mpg at 75 mph or so. When towing a 25' TT (about 5500lbs I think) it would drop to about 10mpg at 65mph. I also towed a sailboat that weighed about the same and I would get 13mpg. The boat was way less windage than the TT so I actually would nudge up to 70 mph at times. When towing towing the TT the wind drag was very noticeable, the faster you go the worse it was.

Like was said before; if you use the truck mostly while not towing then you probably should just live with it for the small percentage of time towing. One thing I would check into though is a transmission cooler. The one on your truck is likely to be really small but there are some good aftermarket choices. I bought one called Tru Cool which is well made and comes in a variety of sizes, if I recall I paid about $50 and put in in myself. Good luck.