Trailering MPG question

[turnbaugh]

I am wondering if something is wrong causing reduced gas mileage.

I pulled my 20 ft enclosed trailer with the wife's Tahoe and got about 9mpg. I thought I would try my friend's Ram 150 5.x Hemi and expected to get better gas mileage.

But guess what? 9mpg.

Does this sound right?

( I even have AirTabs on the trailer)

D

[Stan Clayton]

Dean, over the past decade I have pulled the same 24' enclosed trailer loaded to 8000 lbs with our Ralt Atlantic, spares and tools to the Runoffs at Mid Ohio, Heartland Park and Road America with a '76 E-250 with a carb'd 460 BBF, a 35' Cat 3208 pusher diesel RV and a 2000 Excursion with a 7.3L PSD. The results?

Ford van with a 460 CID carb'd gas engine: 6.5 mpg at 55mph.
Cat 3208 diesel pusher RV at 55 mph: 8 mpg.
Ford Excursion PSD at 70 mph: 10 mpg.

Your mileage may vary...but not by much!

[turnbaugh]

I was doing 65 most of the time. I guess around 9 is as good as it is going to get.

Thanks Stan.

[HazelNut]

my daily driver these days is an 04 dodge ram 2500 with the 5.7 hemi. I get 11mpg on average driving around, without a trailer!!!!!

[Matt King]

My 96 F250 with a gas 460 gets 10-11 mpg unloaded. With a 24-ft enclosed it gets about 8 mpg depending on speed.

[Camadella]

I did an experiment with my Ford diesel 6.4 and my 38' gooseneck trailer - it has instant readout of MPG.

On level ground in Ohio - no hills to affect the reading:

50MPH - 14MPG
55MPH - 14MPG
60MPH - 12MPG
65MPH - 10MPG
70MPH - 9MPG
75MPH - 8MPG

I think it's a lot more a factor of how fast you drive than anything else. I can't stand to go 55MPH - so I use more fuel

Chris C.

[turnbaugh]

Thanks guys. good info. It seems like the best gas mileage towing is from a diesel. From the info it looks an additonal 1-2 mpg from diesel over gas.

[Bob Wright]

Just to add a little more data...

1) Chev duromax diesel w/40ft goosneck: 9mpg @65mph, 6 mpg @75mph
2) Chev duromax w/24ft tag trailer: 9mpg @ 65mph
3) Ford 9000/3408 Cat w/50ft Featherlight: 9mpg @60-65mph, 4gpm with Al Jr driving (foot matted all the time)

There seems to be a pattern here...

[Jon Jeffords]

89 E350 box van w/ 7.3 diesel pulling open trailer at roughly 65 mph: 11 mpg.

[Camadella]

3) Ford 9000/3408 Cat w/50ft Featherlight: 9mpg @60-65mph, 4gpm with Al Jr driving (foot matted all the time)

That's pretty funny.

To maximize fuel usage, I wait until the truck is going down a really big hill, and is going around 95, and then I set the cruise control. Then the thing drives like Al Jr. for the rest of the trip - or at least until you have to stop for fuel, which is soon.

[mike g.]

My 96 F250 with a gas 460 gets 10-11 mpg unloaded. With a 24-ft enclosed it gets about 8 mpg depending on speed.

Matt - I had an early 97 F250 w/ the big gas engine too - I was getting 8-10 towing or not... saw a check engine light come on once, then not on for a while after.. didnt know what was up..

Finally caught the CEL and had the codes read then - O2 sensor. Replaced it and went to 14-15 unloaded...

Apparently a standard issue on these trucks - O2 is bad but the CEL isnt thrown reliably. So if its older than 20k miles you might want to change it.. $40 or so and a huge improvement.

-Mike

[Matt King]

Good tip. Been meaning to do it the last two years!!! CEL is On too. Probably wasted a few hundred in gas for a $40 part!

[mike g.]

Hah, yeah - hope it comes out easy. The PO on mine either put it on or tried to take it off with vice-grips. Had to torch it and bang on it to get it out.

And.. get the one with the longest connector wire at autozone - they will show 3 part numbers... One is 8", one is 12" one is 18. They'll give you the 8 but it wont stretch that far.

[LAJ]

My brother has been towing drag cars for years and as soon as he get a new motorhome likes gas (Ford 460)engines in his motorhomes.First thing he does is pulls the engine ,cleans up the ports on the heads ,in goes a marine camshaft and an aluminum dual plan intake with a 780 holly.After doing this engine goes back in with headers and dual cat exhaust.28 foot motorhome & 2400 lb. car plus 2500 lb. trailor he gets 15 to 18 mpg diving all over central USA with plenty of hills.He says the work pays for it self 10 times over the use of the motor home(he keeps them about 6 to 7 years or 70,000miles.He says the Marine cam is the biggest key to the better gas mileage but it all helps!!
Lee

[Brian]

I'be towing with a dodge Hemi for four years now. It gets 9 to 9.5 mpg, so you are right in the ball park. it's a wind resistance thing, so speed matters a lot. I tow at up to 18K lbs total weight, and aside from slowing down a bit, it does just fine. If you want 350 hp, you need to put the gas in, it's aas simple as that.

Brian

[smcqueen]

Power
The power required to overcome the aerodynamic drag is given by:
Note that the power needed to push an object through a fluid increases as the cube of the velocity. A car cruising on a highway at 50 mph (80 km/h) may require only 10 horsepower (7.5 kW) to overcome air drag, but that same car at 100 mph (160 km/h) requires 80 hp (60 kW). With a doubling of speed the drag (force) quadruples per the formula. Exerting four times the force over a fixed distance produces four times as much work. At twice the speed the work (resulting in displacement over a fixed distance) is done twice as fast. Since power is the rate of doing work, four times the work done in half the time requires eight times the power.


You can't overcome the physics. The diesel thermo cycle is inherantly more efficient than the otto cycle (gasoline engine). With a trailer, your frontal area is about the same no matter what you pull with. The coefficient of drag pretty much sucks and is about the same. So the main driver is velocity. For a given speed, your diesel engine will get better economy. When I swithed from a tag to a gooseneck my milage improved one-half to one mpg because of aero improvements. Obviously headwinds and tailwinds can have a measurable effect.

scott

[SStadel]

Equations, Scott? We don't need no stinking equations!

RFP = CM, but GETA (right foot planted = crap mileage, but good ETA)

RFF = BM, but CETA (right foot feathered = better mileage, but crap ETA)

[Matt King]

Speed costs money--how soon do you want to get there?

[smcqueen]

Steve, I think the proper equation would be:

ETA = RFP/CM squared

[rmccown]

I was told there would be no math.

[TedV]

I have a 97 Suburban K1500 4x4 to get out of my yard.

enclosed trailer loaded or empty at 65mph = 9mpg

open trailer = 12 - 13 mpg speed between 65 to 75mph

On the subject of economy while towing. 4L60 transmission cost about $1500 to get rebuilt with extra goodies tossed in so it might last a little bit longer but it will still go bad even tho GM says you can tow with it. Change fluid often helps. 4L80 will last longer I'm told.

[thomschoon]

I am starting to feel pretty good about my '03 Expedition, gets 10-12 at 65+ towing a 20ft weighing around 4000lbs.

[Rick Ross]

Scott,

I have to ask....what was your source for the very cool mathematical symbols (subscript, exponents, etc.)? Did you use an application such as Maple?

Also, how did you insert the equation into your post? I thought that Apexspeed only supported plain text.

[turnbaugh]

I need an Expedition. I would be happy to drive 60 and get 10-12 mpg.

[ReynardF1000]

If you remove all the stuff you don't really need (I've seen guys use their trailers for storage and just haul 'stuff' to every race, I know it's not easy to know what you'll need, but have a look anyway) you can use a smaller trailer and tow vehicle and really improve your mileage. The other great payback for smaller outfits is parking, turning around and pit space usage.
I bring every tool that is needed for 90% of car work/repair, (and very few tools that may be needed for potential issues) spares for real possibilities and get 18 - 20 MPG with an aluminum trailer and RAV4, V6. This mileage is correct based on several tanks of fuel and not based on values based on a 'mileage race' mentality.
YMMV
Greg

[Brian]

Greg, this may be embarrassing for you, but "manly men" understand that you need to show up with every spare you own, all the tools, some that don't even do anything, and then complain about gas mileage, with the lower the better in terms of boosting the manly factor.

"My 45 foot Prevost with 675 HP and 9 million foot pounds of torque gets 2.3 MPG, but then I'm towing a 29 foot stacker with the Hummer H1 under the race cars so I have a pit vehicle. Yep, the H1 sure works good when the pits really are a pit, as in old quarry..."

Brian

[dereklola]

Ah yes - gas mileage towing a trailer - having lunch with non-technical sales types after I started racing (and towing) one of the sales types asked me what my gas mileage was. Only being used to numbers like 30mpg (good) and 20mpg (not good) they were somewhat apoplectic when I said "Oh averages about 10 I guess". Then one of them asked "Couldn't you improve that by slowing down?" To which I replied "Gee I suppose so - never considered that alternative"

[Albatross]

May I suggest that all of you should simply move closer to the race track that you plan on patronizing the most.

[enjoythetrack]

Adding data:
2008 Ford F250 with 4.10 axle and 5.4L
Towing 5k lbs with Thule V-nose aluminum 18 ft trailer
9.5 mpg including NH/VH hills and valleys.
FYI: normal driving no trailer is 13.5 mpg in VT/NH and when in flat Florida was 17 mpg

[Zcurves]

2004 F-350, 6.0 PSD, 4x4, long bed, crew cab, Dually pulling a 24ft flat front TAG that weighs 7000# loaded. Engine mods include Banks cold air intake and exhaust. Mileage could be worse but if I can't tow it, it doesn't need to be moved.

I get 13/15 mpg city/highway unloaded.

I get anywhere between 9.5 and 11 mpg towing at 70-75 mph. I thought that putting a sloped camper shell would improve the aerodynamics and direct the wind over the front of the trailer. The difference is negligible if there is any increase at all. It does keep my pit bike, bicycles, and spares dry and allows me to walk freely around inside the trailer.

Drafting an 18 wheeler on the interstate (at a safe distance) seems to add 1 mpg.

Also burning a 50/50 blend of biodiesel (B50) for higher Cetane. Smeels like FRENCH FRIES!!!!

[budawe]

2005 250hd swb 2 wheel drive, 20 ft. pace at 6500#. 12.5 to 14 at 62 to 65 mph. If I speed up it goes down really quickly. Have thought about a camper with a kick up, understand it will give 1.5 maybe. That's a payback after about 70,000 miles.

[racer27]

2007 Lincoln Avatior, full time all wheel drive, 16ft. pace at 6200#, 7-9 mph depending on speed and hills. Not towing, avg mpg was 15 MPG, pretty bad for the limited interior space the car had.

Most of poor mpg, due mostly to low rear end gearing and police incepetor high perforamce engine. I've since gotten rid of it, and rent a Chevy Siliverado Pickup when I need to tow.