Gas mileage

roadrunner

Good morning

I have a 2022 TAB s BD, TV 2020 Ford Ranger.

I have noticed several people mention low gas mileage in discussions of other topics but I have not seen a discussion on the gas mileage topic.  Has anyone in the group used a deflector or airfoil on the back of their TV to improve gas mileage?

I have towed a auto of similar weight but much lower profile to the BD and gotten 22 mpg on a 3000 mile trip.  Towing the BD I get anywhere form 17 to 12 mpg depending on how hard the wind is blowing.  This is at 55 to 65 mph.  I am looking for a solution to the "Great Wall of TAB".

Mickerly

Sounds like we are both pulling the same wall.  ; )

kottum

It's all about driving into or with the  wind, wind speed, and vehicle speed on the long trips.  To a lesser degree, terrain with uphill grades.  Not much we can do about terrain or driving into the wind to reach a destination except adjusting routes and schedules.  We can adjust vehicle speed and it makes a great difference.

As for an airfoil, the T@b has a pretty decent profile, rounded in front and tapered in back.  I don't think and airfoil would help much.  Some have said a  pickup topper is slightly better than a tonneau cover.  We have the lighter tonneau which works best for us functionally.  You can improve the air flow by keeping your tow vehicle and trailer clean of gear, no bikes or carriers on the roof of either.

Gas is getting really expensive, diesel over the top.  We need our T@b for our frequent long travels, so we adjust our speed.  55 mph works well if you can budget the time.  Reducing 5 or 10 mph on a day's driving is not a huge penalty, and leaves more money in your wallet.  No gadgets to buy or mess with.

Doug

Sharon_is_SAM

Discussed here:  
https://tab-rv.vanillacommunity.com/discussion/comment/104489#Comment_104489
https://tab-rv.vanillacommunity.com/discussion/1328/gas-mileage/p1

I think that you need a number of those stickie wind deflectors to make a difference.  A big issue is the frontal surface of the TaBs.  

Slim Potatohead uses an old snowboard to gain up to 3 mpg:  https://tab-rv.vanillacommunity.com/discussion/1328/gas-mileage/p1

Viajero

kottum said:

It's all about driving into or with the  wind, wind speed, and vehicle speed on the long trips.  To a lesser degree, terrain with uphill grades.  Not much we can do about terrain or driving into the wind to reach a destination except adjusting routes and schedules.  We can adjust vehicle speed and it makes a great difference.

As for an airfoil, the T@b has a pretty decent profile, rounded in front and tapered in back.  I don't think and airfoil would help much.  Some have said a  pickup topper is slightly better than a tonneau cover.  We have the lighter tonneau which works best for us functionally.  You can improve the air flow by keeping your tow vehicle and trailer clean of gear, no bikes or carriers on the roof of either.

Gas is getting really expensive, diesel over the top.  We need our T@b for our frequent long travels, so we adjust our speed.  55 mph works well if you can budget the time.  Reducing 5 or 10 mph on a day's driving is not a huge penalty, and leaves more money in your wallet.  No gadgets to buy or mess with.

Doug

Totally agree on a couple of points you mentioned Doug.  

First, slow down. We travel at max 90 kmh (55 mph???) and many times less on secondary highways. It makes a huge difference. Set the cruise and relax. 

Second, a truck cap makes a significant difference on smoothing out the aero dynamics. Better than a tonneau for sure, or at least in our experience when we towed with a truck. (We tow with an electric SUV now so it’s been a few years since we towed with our 3/4 ton. 

Two other things that help. Get rid of the vent covers on the roof. I don’t find them that useful to begin with and they are a point of maintenance. 

Last but not least, one of the trailer mag pubs did a little analyzing into the affect of all these raised wheel Boondock type trailers and found they affect both aerodynamics and stability. Some people need them because of where they go etc. But I think some just get them for the looks. 

Anyway, adding everything up might help the whole gas mileage thing. We left that behind us 7 years ago when we switched to electric but I remember well the pain at the pumps. We only started towing electric this year but would recommend it to anyone, although for sure it’s not necessarily the right way to go depending how you roll. 

Stay safe on the road all and enjoy the camping season whatever you are driving. 

mtbmitch

The gap between the TV and the trailer creates a tremendous amount of drag. Also the parasitic drag from the stuff hanging down such as stabilizers along with awnings not faired reduce mpg. As previously stated, vent covers create drag but are easy to replace with something more aero. A good slick wax might help a bit for those of us who tow at higher speeds.

Binghi

If you’re like me, the Great Wall of Tab 400 is the price you pay for being able to stand up straight in the cabin. Slightly smaller diameter tires might help. Slowing down also helps, but no way I’m going to crawl. Based on my experience, towing a trailer burns a lot of gas (or battery charge).

roadrunner

Thank you Sharon_is_SAM for those links and the trip down mpg memory lane.  Based on what I read in those previous mpg discussions, in my opinion, the TAB 320 and 400 have serious wind resistance issues.  Further I respectfully disagree with kottum that "there is not much we can do about driving into the wind".

I did a profile of my Ranger (TV) with my Tab 320s BD attached.  It has been a long time since I have done any fluid flow analysis, so if there are any aerodynamics gurus in the Forum I would appreciate their opinions.  The profile demonstrates that the height of my tonneau cover is a few inches higher than the top of the spare tire and just about the same height as the point where the TAB profile begins its' curvature.  It other words the wind off the back of my truck bed is hitting a vertical flat wall of the TAB.  Further the spare tire and storage box could be causing some turbulence in the approximately 4 feet from the end of the truck bed to the wall of the TAB.  I agree with kottum that a topper would be more advantages than the tonneau cover since it would result in the wind hitting higher on the TAB profile.

I estimate that a deflector on the back end of  of the tonneau cover with an angle of between 30 and 45 degrees would direct the wind to strike the TAB at a point tangent to to its profile.  Any opinions on my idea to reduce wind resistance?

aphillips

@Viajero What electric vehicle are you towing with? 

ClaudeA

I just finished a 14000KMS (8000Miles) trip through the mid and northwest U.S. My average speed is probably about 60mph. Obviously a lot of climbing. I was consistently between 11 to 13 L/100kms (18 to 20 US mpg). I was towing with a 2022 Toyota Sienna Hybrid. I was a little concerned about the small engine in the Hybrid but it performed amazingly. Thanks to Pretzel14 for his info on his Highlander Hybrid.

CharlieRN

Viajero said:

Totally agree on a couple of points you mentioned Doug.  

First, slow down. We travel at max 90 kmh (55 mph???) and many times less on secondary highways. It makes a huge difference. Set the cruise and relax. 

Second, a truck cap makes a significant difference on smoothing out the aero dynamics. Better than a tonneau for sure, or at least in our experience when we towed with a truck. (We tow with an electric SUV now so it’s been a few years since we towed with our 3/4 ton. 

Two other things that help. Get rid of the vent covers on the roof. I don’t find them that useful to begin with and they are a point of maintenance. 

Last but not least, one of the trailer mag pubs did a little analyzing into the affect of all these raised wheel Boondock type trailers and found they affect both aerodynamics and stability. Some people need them because of where they go etc. But I think some just get them for the looks. 

Anyway, adding everything up might help the whole gas mileage thing. We left that behind us 7 years ago when we switched to electric but I remember well the pain at the pumps. We only started towing electric this year but would recommend it to anyone, although for sure it’s not necessarily the right way to go depending how you roll. 

Stay safe on the road all and enjoy the camping season whatever you are driving. 

I've been following the issue of range while towing with an EV closely after putting a pre-order in place for a  Rivian more than two years ago. Data on the subject had been sparse, but with the surge in EV sales, much more has become available in recent month. It was surprising (to me at least), to learn that weight has a relatively small effect on range and that the primary determinant is drag.

Based on what I've read, I anticipate the R1T will be able to travel in the range of 1.2 to 1.3 miles per kWH while towing my 320S BD.  Using the common 80%/20% SOC parameters, the 180 kWh battery pack of the Max model I've configured should give an effective range of 138 - 150 miles. Those numbers will be reduced considerably in hot or cold weather, or when windy however.

That kind of range is quite a bit less than most ICE vehicles offer when towing something like the T@B. I can comfortably travel 250 miles before refueling while towing my T@B with my Telluride for example, with high confidence that there will be a service station available when the needle approaches empty, regardless of where I am. The combination of reduced range, and uncertainty about the ability to charge are tough challenges to more widespread EV adoption, particularly when towing is in the use mix.

I think I'd be OK with that relatively meager range of the R1T, if the charging infrastructure was a bit more robust. We are largely there on/near both coasts, and getting close in may other parts of the country. But looking at the charging maps of North America, there is a long way to go in more the remote areas, particularly Canada. There is of course the potential to plug in the EV at campsites with hookups, but 110v charging is agonizingly slow (days, not hours) and in any event, that kind of defeats the purpose of having a Boondock.

I think there's a good chance that the charging infrastructure will be considerably more robust before the scheduled delivery of the R1T, which will likely not be before early 2024. I'm betting that the four year wait for the Rivian will be worth it, but if not, there's always "Bring a Trailer."

B11

Just returned from our trip to Pictured Rocks National Lakeshore. Our TV is a 2022 F150 pulling a 400bd.

On the way to our site traveling northeast, we averaged close to 15mpg traveling an average of 65mph with what I could tell was a tailwind.

On the way home traveling southwest, we averaged a paltry 8.7mpg at an average speed of 62mph with most likely a headwind.

I noticed on the way northeast our TV would regularly shift to a lower gear(either 9 or 10) while on the way home the F150 would sit in 8th gear. 

Not a significant amount of data to draw clear conclusions but considering the data we have, I'd make the claim that the wind made a significant difference in mpg over the course of the total trip. I was quite shocked and displeased with the performance of the setup in handling the headwind. I did have higher expectations of a teardrop-shaped camper's ability to be more aerodynamic. I do realize I have no comparative data pulling a non-teardrop camper. 

Viajero

aphillips said:

@Viajero What electric vehicle are you towing with? 

Tesla model Y

Denny16

The TaB seems it would have less of an air drag, due to its sloping front curve design, than older flat front trailers like the can of ham style trailers, with their mostly large flat front wall going down the road.  I notice the TaB400 pulls better in a head wind then does similar size cargo trailers, with mostly a flat front, I have towed.  Yes any headwind drag is going to reduce you mpg, even just driving an average 1/2-ton truck without towing a trailer is going to drop its mpg.  The curved shape should reduce the frontal drag area over a flat surface the same overall height.a 4x4 foot surface is not twice the size of a 2x2 foot area, but 4 times.  So a 4x4 surface will have four times the drag effect over a 2x2 foot surface.

The faster you tow, the more effect the drag will have as it increases the relative speed of the head wind (actual speed of wind plus speed of the vehicle).
 Cheers 

MuttonChops

roadrunner said:

I have a 2022 TAB s BD, TV 2020 Ford Ranger. . . .
Towing the BD I get anywhere from 17 to 12 mpg depending on how hard the wind is blowing.
This is at 55 to 65 mph.

First reaction was that is about the same MPG range reported by a few Ranger + 400 owners.
It is also near my V6 no-turbo Colorado MPG at over 30K+miles 320S (hand calculated not TV computer) towing which is in the 13-16 range with typical speed of 62 MPH.

Trailer frontal area and trailer drag coefficient (shape) are the major factors for MPG baseline differences between different trailer brands/models with the same/similar TV.

For any given TV + trailer; Your driving speed is by far the greatest factor for MPG.

For example:
     TaB 400 frontal area is  ~ 15% larger than a Tab 320S
     For both models the drag resistance difference driving at 50 MPH and 60 MPH is ~ 31% larger.

There is very little we can do to reduce the drag coefficient of the trailer.
  We can control some of the TV+trailer drag with TV types that deflect air above the trailer but we can't really reduce the TV rear to trailer front gap, the trailer undercarriage, etc.  On commercial big rigs  air deflectors, etc that reduce the drag coefficient do provide minor cost effective MPG improvements but for them the weight is also a much more important factor.

When shopping for my 320S I did some 'for educational use only' air flow 2D modeling.
After seeing how the 320 BD rear tire rack impacted air flow I decided to just order the lifted axle.

A Reference Point Only

CharlieRN

The images of your modeling are very interesting @MuttonChops. Fluid dynamics is not something I have a great understanding of, but it looks like the results between the two models show some pluses and minuses to each. The 320 seems to have less turbulence at its front, the area from the tailgate to the trailer. The 320 also seems to have a smoother airflow at its trailing edge, even with the rear rack. The 400 seems to have more turbulence at its front and trailing edge, but looks a touch slipperier overall, perhaps because of the more rounded overall profile.

Are those conclusions correct? Are they what led you to choose the 320 over the 400?

Some final related thoughts and questions: It looks like the combination of an SUV (or a pickup with a cap) with either T@B model may present a better aerodynamic profile due to the greater height at TV at its rear. Is that a reasonable assumption? And if you're really looking to get the most mileage/range out of your TV-camper combo, you want to go low profile. Do we conclude that something like the Alto Condo Safari R173, that collapses so that its 83-1/2 inch rounded top protrudes minimally above the top of a pick-up or SUV roof, could result in substantially less of a mileage/range penalty?

MuttonChops

CharlieRN said:

The images of your modeling are very interesting @MuttonChops. Fluid dynamics is not something I have a great understanding of, but it looks like the results between the two models show some pluses and minuses to each. . . .
Are those conclusions correct?

I'm also not knowledgeable at a detailed technical level of fluid dynamics.  Just did web research to get drag coefficient ranges and locate a simulator - - - which runs with most of it's creator defaults.
So your guesses are as good as mine.

CharlieRN said:

Are they what led you to choose the 320 over the 400?

No, at the time of purchase the 400 was too new and too large for my needs.
It is now on my maybe-in-the-future dream list.
I also ordered BD 'package items' to create a BD-Lite trailer to save dollars before BD-Lite was an option.
>The flow simulation was just extra 'I did good' back patting.

CharlieRN said:

t looks like the combination of an SUV (or a pickup with a cap) with either T@B model may present a better aerodynamic profile due to the greater height at TV at its rear. Is that a reasonable assumption? And if you're really looking to get the most mileage/range out of your TV-camper combo, you want to go low profile.

I would believe you are correct.  Several smaller-van-style TV owners report better MPG data than the pick-up truck owners.  Those newer van's also have air foils along their trailing edge.  But I use a Truck TV for hauling bikes and camping stuff + as my day-trip 4x4 adventure machine.

CharlieRN said:

. . .  conclude that something like the Alto Condo Safari R173, that collapses so that its 83-1/2 inch rounded top protrudes minimally above the top of a pick-up or SUV roof, could result in substantially less of a mileage/range penalty?

Alto R173 frontal area is 48 vs. 320S at 51.5 and 400 at 60.6 sq-feet
So I would expect it could have slightly better MPG compared to a TaB for the same TV.

SLJ

After one year of watching and comparing, my MPG increases by 1.5-2 miles per gallon at 60-65 when I have both our canoes on top of the SUV when pulling my 320S BD.

schwartzki

So I had 2 bikes in the bed and my Thule rack fairing mounted right in front of the bikes to keep the bugs off of them for my most recent 2week trip and that actually increased my trip fuel economy to just shy of 12mpg. I also slowed down a few mph to around 65 on this trip. This is the best photo of my setup I have from house security camera

subkron

@schwartzki I was also thinking a fairing would help. When you say increased to 12, what was it before? Also I'm thinking the speed reduction may have been a larger factor. 

SLJ

Speed reduction is a huge factor. Besides, the speed limit for towing a camper is 65 MPH in most States no matter what the higher posted speed limit is. Some States are even lower.

Denny16

In California it is 55mph, and I try to keep my speed at a max of 60mph or lower.  I get the best fuel economy at 60 or under,  towing or not.
Cheers

Passport

I try to drive at a slower speed while towing the T@B and invariably, there is a line of vehicles behind me so I try and pull over as a courtesy to let them pass at the first opportunity.  One time that I can remember, I pulled over in a little cut-off and wham!  Hit a pothole with the tV and T@B.  This isn't  too good for the TV or T@B!  It's seems like a trial of sorts trying to drive slower but I'm going to continue, it increases the MPG.  I usually obtain 14.9 or so at lower speed and 13.6 driving like a nut.

CharlieRN

SLJ said:

After one year of watching and comparing, my MPG increases by 1.5-2 miles per gallon at 60-65 when I have both our canoes

Hmm, this make me think I'm making a mistake leaving my kayak behind . . .

Edit: While we don't often need the extra storage, it may be worth putting the Thule cargo box in place. We're heading out on short trip in a couple of weeks and a longer one next month. I think I'll experiment, leaving it off for Trip 1 and putting it in place for Trip 2.

GatorEgg

I made two identical back to back trips back in 2019 towing my ‘18 320 BD.  This was just after purchasing my ‘19 Tacoma.  During the first trip I had ordered a ARE Mx high rise, but not received it in time for the trip.  Second trip I had topper and picked up about 2.5 mpg on highway sections.  I average between 14.5-15 mpg normally towing my Boondock.  This is with a 4x4 Tacoma and taller Boondock model.

tybladesmith

@SLJ, I saw a similar 1.5 - 2.0 MPG increase with two 18' kayaks on top of TV with Van and Jeep Grand Cherokee.

qhumberd

Just finished a 5 day lake trip with this setup and we were at 12 MPG on nearly all 2 lane roads and no speeds over 65 MPG. I see no decrease in MPG with the boats. I agree that speed is the single biggest factor in our MPG with our Tundra.

d_v

@Viajero What do the top of you fans look like with the covers off, do the covers just pop off? What do you do about rain? I am towing with a Model 3 and trying to get every last mile of range. 

manyman297

It's interesting that even larger trucks like the Tundra average about the same as the Tacoma. I would expect the Tundra to do better but maybe the V8 cancels a lot out?

schwartzki

I changed my tow vehicle to a diesel and now averaging 14-16mpg going 70-75 on the highway (wind dependent) State highways where limit is 55-60 I see 19mpg.

pak

Our TV is a 2014 f-150, 5.0 4wd, supercab with a topper. I put some stick on votex generators on the rear of the topper(sides and top). Primary purpose was to keep the back of the vehicle clear of the fine dust we have on our county road. The VGs worked well in this application. Secondary I was hoping to improve my gas milage. Over time I have enjoyed almost a 1 mpg improvement in mpg both as  single vehicle and towing our 320CS-S. The VGs help keep the wind coming off the rear of the vehicle organized and reduces the back pressure directly behind the vehicle. When towing there is less back pressure between the TV and T@B. I am still pondering about putting VGs on the T@B.