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Minnie's Mate · 06-05-2007, 10:01 AM

Quote:

Originally Posted by AgZep

MM,

1 mpg? Or do you mean 1 mpg different than my figures?

There's no practical way to test precisely, but I'm really curious to see how speed relates to fuel consumption. I'm sure a diesel does better whether towing or not, but I wonder if there's a different sensitivity to speed between diesels and gassers.

I was just looking at a recent Trailer Life test of a Nissan Pathfinder towing an SOB about the same size as our Airstream. The Pathfinder got 8.8 while towing, much lower than we get with an 8.1 gas V8 and a drastically heavier rig. I suspect the Pathfinder engine was working really hard under the load.

My F-250 has a trip computer that calculates fuel consumption. If I tow at 75 MPH on the interstate I get 11.6 MPG's. If I tow at 70 MPH, I get 12.2 MPG's. If I tow at 65 MPH, I get 12.4 MPG's. My truck shifts into its final gear at approximately 63 MPH so I don't tow under about 65 MPH on the interstate. My RPM's are the same at 75 MPH as they are at 55 MPH. I have calculated the mileage manually and come up with virtually the same mileage as the trip computer. I keep a close watch on my transmission and water temp gages when I'm towing in the mountains. When I tow on two lane roads and undivided four lane highways, I always tow at the posted speed limit no matter what that speed is.

BTW, the table referenced above is a little askew. In Georgia, the speed limit for trailers is as posted. The Max Tow Speed is 55, but that is for tractor trailers and I have never seen it enforced.

Airstream 4 · 06-11-2007, 04:34 PM

We are towing a 1990, 34' Airstream limited and our speed is 55 mph. Seen to many RV's and tow vehicles in pieces off the road because of high speeds and improper hitches/sway bars. My 3/4 ton diesel Ford, 6 speed standard just loves it. Please drive carefully. Happy travelling, Ken

Minnie's Mate · 06-12-2007, 07:18 AM

Welcome to the forums Ken. Glad you found us and hope to see many post from you in the future.

Glenn G · 01-27-2008, 01:06 AM

I tow at 65 I get under 12 If I tow at 55 I get almost 15 mpg on gas and its just a more pleasent drive. 55 is the speed limit in CA. If I'm going to have a good time just crusin' it's the right speed. Empty (no tow) to Las Vages and back at high speed (70-75) I get 19.5.

RDM16CCD · 01-27-2008, 03:06 AM

I voted 60 - but it's really more like 62 or 63. My Dodge Cummins feels 'in the groove' towing at those speeds. It certainly could go faster, but things feel right.

Not towing, the groove is 68 mph.

ROBERTSUNRUS · 01-27-2008, 10:21 PM

Hi, I tow at 25 MPH, in school zones, when children are present.

FreshAir · 01-27-2008, 11:33 PM

I tow at 65 unless doorgunner is behind me on the radio asking me to slow down

.

**Action** · 01-28-2008, 04:40 AM

It's 15mph in AZ.
>>>>>>>>>>>>>>Action

Minnie's Mate · 07-07-2008, 10:31 AM

In December I traded trucks and purchased a 2008 F-250 with the new power stroke diesel. The mileage with and without the Airstream in tow is considerably less than that of the '05. Unfortunately, I had to start towing almost immediately with approximately 1,000 miles on the truck when I first towed the Airstream. I was getting 9.6 MPG's at 75 vs. 12.6 with my '05. I requested an update on the programming with a tilt toward towing at that speed. That got me an extra 1 MPG to 10.6 MPG's.

This past week I decided to tow at 70 to see if there would be a difference. I towed 455 miles on the interstate only stopping for one meal and once for fuel and another for a rest room break. Other than that I kept the cruise control on 70. I got 10.5 MPG's. I actually lost .1 MPG's by decreasing my speed by 5 MPH. That is not scientific of course and there were probably other factors that would have impacted the fuel mileage, but I don't know what they could have been. For once I didn't have to drive through any significant amount of rain that would have slowed me down as is the norm on these trips. I'm not saying that justifies the speed, but this is a stretch of interstate that I travel 4-5 times a year and know where to take it easy on the rough sections (heading south) and where I can safely go faster. Traveling the same stretch of interstate is so boring is the main reason I go with the flow. That extra 5 MPH trims nearly 45 minutes off the travel time and that's a lot of time when you are fatigued from sitting behind the wheel for 6 plus hours with a bad back and looking at the physical demands on that aching back with all the bending over to set up camp.

With the Airstream in tow, the main problem is finding an opening to pass cars in the right hand lane that go 65 or slower, not to mention semi's that slow down on every hill and speed up on the down side. All the other traffic wants to go 80 or more and going 75 seems like I am in their way when I try to pass. Also, the right hand lane is dominated by tractor/trailers and they beat up the road surface pretty badly so I feel the center lane is less stress on the tow rig/Airstream combination. As my Airstream tires age I will slow down and may do that anyway to save on fuel...if I can find a speed that will save any. I do plan on replacing my tires earlier than most people recommend just to be on the safe side.

fotochop · 07-07-2008, 10:44 AM

- as a Zen master I find journey as interesting as the destination ;-)

OK, the real reason I tow at 55 is because of my 8 yr. old in the back seat...and my single axle trailer...and the mileage...and...

Mikethefixit · 07-07-2008, 01:56 PM

Minnies Mate
What rear end ratio does that thing have? I have a F350 PowerStroke 7.3 with a 3:73 ratio and an getting about 17mpg average. Now we are both retired but when we did the two short trips this yr The average included a week of city driving also. If your ratio is 4:10 U will never get good mileage. U need the RPM's at 1650 to 1850 for mileage.
U can get chips for that computer that will not affect the warrenty.
But don't really expect great mileage before U reach 60K miles is about the time that engine is broke in. Be more careful on the jack-rabbit starts and trying to reach terminal velocity in 6 seconds. Diesels don't come up to speed like gas engines. Thus when U do this little meaningless things they adversely affect fuel mileage and 60 to 65 mph max tow speeds will increase it also.
I'm not just trying to blow smoke at ya, I have 45 yrs with diesels OVER THE ROAD not including my young yrs on the farm.
Best of luck to U
Roger

Minnie's Mate · 07-14-2008, 01:32 PM

Thanks for the advise Roger. I am not real familiar with diesels as this is only my second. My first didn't have the initial get up and go that this one does, but then it only had one turbo and not the twins that this one has. I know part of the loss of mileage is the particulate burner in the exhaust system and part of it is just the ULSD fuel. My first diesel was a 6.0 and tach'ed the same pulling the Airstream at 75 as it did at 55 because of the final shift point. I haven't towed as much with this one yet so I haven't found it's sweet spot.

Right after I bought this truck, I stored my Airstream in central Florida where all of our trips for the first half of the year would be so I wouldn't have to drag it over the same roads time and time again. This turns out to have saved about $100/trip over four trips plus one to two hours on each leg of each trip. We have a couple of rallies coming up here in Georgia plus the Labor Day Weekend at a nearby State Park so I brought it back after this last trip to have for those.

I have reservations about the programmers that are available on the aftermarket. I'm not familiar with replacement chips other than having seen motorhomes advertised with Banks chip sets along with Banks exhaust modifications and Banks air intake systems. I assume you can get new chips from Ford (?). I did ask the dealer's shop to update the programming several months ago and that seemed to raise my mileage from around 9.6 to 10.5 MPG's.

I have the 3.73 rear end...or at least that is what the paper work says and it is 2WD and not 4WD. With my first diesel truck I was getting between 19-20 MPG's on my daily commute (again 3.73 2WD). With this truck I get around 17. I figure I lost 2 MPG's both towing and non-towing. But my back sure appreciates the re-designed seats of this truck over those that were in my '05.

norsea · 07-14-2008, 05:11 PM

Quote:

Originally Posted by Minnie's Mate

Thanks for the advise Roger. I am not real familiar with diesels as this is only my second. My first didn't have the initial get up and go that this one does, but then it only had one turbo and not the twins that this one has. I know part of the loss of mileage is the particulate burner in the exhaust system and part of it is just the ULSD fuel. My first diesel was a 6.0 and tach'ed the same pulling the Airstream at 75 as it did at 55 because of the final shift point. I haven't towed as much with this one yet so I haven't found it's sweet spot.

Right after I bought this truck, I stored my Airstream in central Florida where all of our trips for the first half of the year would be so I wouldn't have to drag it over the same roads time and time again. This turns out to have saved about $100/trip over four trips plus one to two hours on each leg of each trip. We have a couple of rallies coming up here in Georgia plus the Labor Day Weekend at a nearby State Park so I brought it back after this last trip to have for those.

I have reservations about the programmers that are available on the aftermarket. I'm not familiar with replacement chips other than having seen motorhomes advertised with Banks chip sets along with Banks exhaust modifications and Banks air intake systems. I assume you can get new chips from Ford (?). I did ask the dealer's shop to update the programming several months ago and that seemed to raise my mileage from around 9.6 to 10.5 MPG's.

I have the 3.73 rear end...or at least that is what the paper work says and it is 2WD and not 4WD. With my first diesel truck I was getting between 19-20 MPG's on my daily commute (again 3.73 2WD). With this truck I get around 17. I figure I lost 2 MPG's both towing and non-towing. But my back sure appreciates the re-designed seats of this truck over those that were in my '05.

Hi Minnies Mate,

I too am the proud owner of a new F250 Powerstroke. I too have the 3.73 rear end but I have the 6 speed manual gear box.

I can say, based on my own experience, that the Lie-O-Meter that calculates fuel mileage does not work worth a hoot.

I have recorded mileage and gallons purchased since we bought the truck new some 17,000+ miles ago last November. We've been across the country from Oregon to New Jersey, south to Florida then west to San Diego and north back to Oregon. NEVER (strong word) has the Lie-O-Meter come close to the computation of miles divided by gallons of fuel pumped into the tank.

The Lie-O-Meter ALWAYS tells me I am getting MORE MPG than the actual computations produce. That makes matters even worse if you are not happy with the fuel mileage.

I spent a lot of time hanging out on Ford Powerstroke forums learning as much as I could about the new Ford diesel prior to our purchase. From what I have read, I would be very reluctant to change anything associated with the emissions controls on these new vehicles. It has been stated by those who have changed the computer chips in their vehicles that Ford voided their power train warranty as soon as this was discovered.

Apparently the new vehicles do have the capability to record when a chip is taken out and/or put in. I understand that previous year models did not have this capability. It also notes that a non Ford chip was inserted.

The same is true for those who made changes to the exhaust.

So, I would be VERY conservative about making modifications of this nature. I have asked my local service department folks about doing changes of this nature and they have stated that the voiding of the power train warranty is a very real issue.

Apparently the EPA is very serious about ensuring that clean air wins. I could be wrong.

Jim

Minnie's Mate · 07-15-2008, 02:56 PM

I've always felt that the engineers in the white coats at the design centers knew what was the best compromise on issues of fuel/air mix and figured the same was true with diesels so I really didn't feel comfortable with aftermarket programmers. A buddy of mine kept telling me I should get one for my '05. He told me it would make my '05 sing and dance and do all kind of special things, and I told him I wasn't going to do anything 'till the warranty ran out and then I'd think about it...not. Well, I traded before the warranty ran out.

Chips are a whole new thing for me. I know nothing about them or how they would be different from the programmers. I have 15K miles on my truck (we've done a lot of camping in central Florida already this year @ 900+ miles each trip) so I still have a ways to go on the warranty and I'm not going to do anything to jeopardize that. I'll have to do a lot of research before I make any changes to what could be a potential $5K transmission job or $10K or more engine job. I don't know for sure what they cost to replace, but the numbers I've heard are really scary.

Fishbowl · 12-29-2008, 02:27 PM

We go at 65mph, hills excluded with a Dodge Dakota and 1970 25' Caravanner. Good trailer brakes and tires, equalizers and sway bars advised. Bad roads dump 10-15 mph immediately.

ts8501 · 12-29-2008, 02:37 PM

Our 34' Excella is towed in the 65-70 range. It just feels right at that speed, and although I can go over 70 (and have), it just feels better below 70.

ridgerunner · 01-23-2009, 10:29 PM

I have just been reading through these posts. Our tow vehicle is an 88 Suburban with a 454 engine and we could pull that lil ol airstream so fast all you would see is a silver streak. BUT, coming from a long line of truckers, I kind of follow the "slow it down and get there alive rule". There are just too many variables that are out of a drivers control. So , to answer the original question that started this thread, I try to go about 10 mph UNDER the posted limit. That limit is for a passenger vehicle, on dry roads under perfect conditions. I figure I'm driving a tank, pulling a missle and I am probably tired, slower is better.

HeadnOut · 01-27-2009, 04:27 PM

pulling with an 05' F-250 V8...try to stay 60 to 65 to get the best gas mileage
@ 13 mpg

Ahab · 01-28-2009, 08:51 AM

We also try to stay 60-65mph and get 14-18mpg towing with the Ridgeline.

shermantic · 02-08-2009, 08:58 AM

I am hammer down all the time! AS trailers so well I have seen 90 on the beltway in Chacogo and DC LOL I have had lots of Chevy trucks and It seems once you rip out the factory junk tranny and buy a good one then you are good to tow in all 4 gears lol