Gas mileage when towing with big motors

[Dimitri-2000X-Tampa]

I keep seeing these posts from people with big V8 trucks that say they are getting like 16-17 mpg towing and that it doesn't vary much when they are not towing. Is that really true? I mean, no BS here with trying to be loyal to your truck and exagerating. Do you really measure how much gas you put in at the beginning/end of a trip and get that kind of mileage?

I'm just curious because with my V8 sequoia, I don't think I've ever gotten more than 10mpg towing...and that is on a good day with a tailwind. On a bad day, with lots of stops and starts, it can go down to about 8.8 mpg...the mean is probably around 9.5. And I'm pretty much almost always running the A/C too...and staying right about at the speed limit.

And the other thing is that the mileage is a good bit better when I'm not towing...pretty consistently 13-15 in the city and 17-18 on the highway (typically a little faster than speed limit). Now granted, my rig is not lightweight, I have most every known goodie modded into my Mac including a water tank, microwave, 2 batteries, 2 anchors, 2-3 gas tanks, every electronic gizmo known to man, and I usually travel around provisioned for 5 people on board and all their stuff. That along with an 1100 pound double axle trailer probably puts my rig close to 4500 lbs but that is just a guess...but its no lightweight rig for a Mac, thats for sure.

So I'm just wondering what are these big trucks that can get almost as good mileage towing as not towing? Are they diesel or gas powered? And how much weight (total payload) do you think you are pulling around?

[Obelix]

I averaged about 11.5 mpg going speed limit without the A/C running and with the full boat-cover mounted on last years cross-country trip (~2850 miles) towing my with my 5.4l V8 RAM 1500 . We get 15-16 mpg on the freeway at 70mph when not towing.

Obelix

[Dimitri-2000X-Tampa]

That's an interesting point Obelix...and I don't think I've ever seen anyone with a cover that they could trailer with at 70mph...do you have a picture of it? Was it custom made?

Theoretically, that must cut your air drag quite a bit. The longest I've trailered in one trip was about 400 miles each way to Pensacola early last November. I remember the leading edges of my spreaders just being covered with plastered bugs and it made me wonder how much air drag all that stuff up top was causing. Afterall, the big truckers frequently cover up their irregular shaped cargos (including big sailboats) with some sort of shrinkwrap'y kind of stuff.

I wonder how much your mileage might go down without the cover...

[Obelix]

Here are two pics after finishing the trip.



Obelix

[Baerkanu]

I've got a 2011 GMC Denali dually with a Duramax -

Empty I'll get just under 17 mph on the highway at 75 mph, I've seen over 20 mpg at 50-55 empty. Towing the Mac, I get between 13 and 14 mph at 70-ish mph and I can't feel it.

I've got a truck camper that weighs in at 4,500 lbs loaded - with that and the Mac behind, I'm at 10-11 mpg at 70 mph. With the camper alone, 11 mpg. Once I have the camper down, the weight of the trailer doesn't make much difference - I've got a horse trailer grossing over 10,000 lbs, and with the camper, I'm still at 10-11 mpg.

- Clay

[Azzarac]

My mileage varies depending on where and what I'm towing. A couple years ago we towed the RV with our H2 with a 6.0L V8 out to the Oregon coast. Across the plains we averaged 15 mpg all the way to the Rockies. Once we got into the mountains I expected our mileage to drop drastically, but the opposite occurred. By the time we got into Oregon we were averaging 19 mpg. Our camper weighs about the same as the , however, with the higher profile of the , we tend to get a bit lower mpg when towing it. When I brought it back from Vegas we were still averaging 15 but when we crossed into Oklahoma mileage dropped to 10. I wonder if different zones of the US have different blends of fuel that drastically effect mileage. I have found that for whatever reason the H2 will almost always get as good or better mileage when towing the camper than when not. Go figure.

Fair winds all! The Great Thaw is on its way!
Cpt. Azzarac
S/V Chameleon
Follow Chameleon's travels at: http://svchameleon.weebly.com/

[Russ]

I've never calculated the mileage, but my Dodge Ram V8 burns a LOT more fuel when towing.

When I towed my old boat with the Sienna van (V6) it would go through a tank of gas back and forth, and about half that otherwise.

[NiceAft]

Dimitri-2000X-Tampa ,

I've got a 2011 AWD Acadia with a six cylinder engine. When towing Nice Aft to the Adirondack mountains, I get about the same as you do while towing. Without towing, it's not a problem to get 21 on the flatlands at highway speeds.

Ray

[Y.B.Normal]

I have 2006 Merc Montaineer w/ V-8, I got 8-10 mpg on my trip from Wisconsin to the North Channel (Lake Huron).
Normally I get ~17-18 mpg when not towing.

[DaveB]

I always ck my gas milage towing to the Keys and get 11.8-12.2 mpg towing the Mac. at 4500 lbs total. Thats with a 1999 f150 extended cab with a stadard trans. 4.2 liter V6 @202 hp.
I cruise 60- 65 mph.
I am interested in getting a new F150 with the 3.7 liter V6 , 302 hp. Empty it gets 17 city and 23 highway, compared to 15 city and 20 highway on 4.2 liter truck.
Dodge just came out with a V6 3.6 liter 305 hp and gets 18/25. I can't find a tork chart for both of these newer engines and would like to see them at 1000-2500 rpm.
Dave

[Sumner]

'99 Suburban with the 5.7 Vortec V-8. Not towing at 65 right at 17 mpg. Towing....



...the trailer above loaded to the top and with the top in the up position 14-15. The Mac going...



...to Canada with the single axle 12 mpg and lots of mountains and high elevation. With the second axle and other mods...



...that added weight and the Suburban fill to the top going to and from Florida (first part of the trip high elevation and hills and second half pretty flat and sea level) 10 to 11 mpg. 2200 miles each way. I figure the second axle cost us about 1-2 mpg but would never go back to one axle.

The new generation Chevy/GMC's with the LS style motors get a little better gas mileage I believe.

It takes so much power to move something so even small motors need the same energy if you are pulling a load. Our '99 Buick gets a consistent 30 mpg not towing on the highway (24 around town), but with the trailer in the first picture it drops to about 15 mpg or about the same as towing it with the Suburban,

Sum

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[1st Sail]

2001 Yukon XL, 5.3L V8, 3:73 towing package, 65-70mph interstate, 10-11 mpg.

[Dimitri-2000X-Tampa]

Wow, some great information in all your responses!

Surprised that Clay's dually does so well, I would think that extra set of wheels/tires would add some drag...and wow, pulling 10K trailer and 4500 lb camper and still better than my mileage by 10%.

And also surprised about Azzarac's H2 getting 15mpg with a 6L V8, I wonder how it can do so well. But this drop to 10mpg on part of a trip seems strange. I wouldn't think the potency of gasoline could vary that much, unless it had water in it or something.

Quite a few other folks get about the same as me so that's reassuring. In some cases like NiceAft, the v6's do about as bad gas mileage wise as a V8 but in some other cases like Dave, the V6's are doing close to 20% better than me. I suppose the V6 vehicles are lighter weight than the V8 so it kind of makes sense that they may be slightly more efficient although its probably more wear and tear on the engine versus a V8. So, many folks are about same as me and quite a few slightly better in the 10-20% range, not that much difference between newer and older vehicles (and my Sequoia is 2002 model), only a couple folks that seem to get much better mileage in the 40-50% better range, even with really big V8's like that H2.

So what is the key here? Sumner brings up a very good point about the number of axles. I have a one year old 2-axle trailer which rides very nice, but it does make sense both from a mechanical drag perspective as well as a weight perspective that it would use more gas. Afterall, my dual axle is more than 400 lbs heavier than my original Mac single axle. I never trailered my single axle very far since it was rusting out and therefore did not pay much attention to the mpg. So what about you guys getting the really good mileage above 12mpg, are you towing single axle or tandem axle trailers?

[mastreb]

I think I can give some perspective regarding gas vs. diesel engines.

My tow beast was a Mercedes Benz 450GL (2007), 4.5L naturally aspirated gas engine. 0-60=7.1s

14 MPG city typical for our use.
18 MPG highway on long interstate trips.
15 MPG typical towing Mac 26M @ 65mph

Replaced it with a Mercedes Benz 350GL (2011), 3.5L turbodiesel. 0-60=10.0s. Exactly the same truck, different engine.

18MPG typical city
26MPG highway on long interstate trips.
21MPG typical towing the boat @ 65mph

We >really< love the diesel. Except that they replaced the spare tire with a CA compliant diesel emissions system that injects urea into the catalytic converter to fully combust particulates so we have to run $550 per tire 20" run-flats. A difficult lesson in Moab UT. Also difficult to pay $120 per 2L refill of a chemical I happen to know that I can buy 100L. of for $50. Sometimes knowing the chemistry is a bad thing.

Matt

[Dimitri-2000X-Tampa]

Great mileage Matt....another variable that certainly makes a big difference when towing is speed. Now that I have that shiny new tandem axle, it pretty much drives like a dream so I don't really slow down much, but there is a good possibility that if I didn't have a (trailer sized) lead foot, I could get up there around 11mpg as well. In fact now that I think about it, when I came back from the Keys via US41 instead of I-75, I think I was getting around 11mpg on that segment at more like 55-65 kinds of speeds without many stops...so slowing down 5-10 mph very well could be saving 1-2 mpg.

So it seems that some vehicles are clearly more efficient towing than others, but to compare apples to apples, we have to peg some variables like tow speed, single axle versus double, diesel versus gas and probably A/C versus no A/C as well. I wonder how much difference the A/C makes, but having towed my Mac exclusively in Florida, I don't have too much opportunity to turn it off.