Question on Tow Haul operation & mpg info - Montana Owners Club

David and Jo-Anna · 05-01-2007, 01:52 PM

Took our Big Sky out on our second trip with our 2007 F350 6.0L PSD. this was the first real test of the truck since our maiden voyage two weeks ago was just a short trip to a campground close to the dealer. And this was the first real test for me as a newbie driver since I've never previously pulled anything with a pickup--or any other truck.

We were going up and down lots of hills on our way thru the Blue Ridge Mountains to the Shenandoah Valley. The F350 did fine pulling the Big Sky up the hills, but I was surprised how it operated going down the hills. I had it in Tow Haul mode in the hills and found that, if I tried to let it coast down the hills, the engine revved up to high rpms (over 3500 rpms). Is that how the Tow Haul feature normally operates? And if so, is there anything I should be doing to keep from overtaxing the engine other than giving the brakes a solid push periodically to slow the truck down?

FYI, I also enjoyed playing with the mpg chip in the truck trying to see what sort of mileage I would get when towing. I was getting about 9 mpg going up and down the hills and over 13 mph when I got on the interstate. After dropping the rig off at the dealers for some warranty work, I reset the mpg gauge and took the interstate home. Driving on cruise control on fairly level terrain at 60-65 mph, the mpg chip was telling me I was getting up to 19.6 mpg up until the time I hit rush hour traffic and started going bumper to bumper. Is that a real number? Normally, I've been getting 14-15 mpg in a mixture of driving on the highway and the city streets. Just couldn't beleive it could get over 19 mpg under any circumstances.

bsmeaton · 05-01-2007, 02:02 PM

David -

You've got the right answer - A solid push to slow the rig down rather than a steady ride on the brakes.

I try to keep mine around 3,000 RPM but will let it run up around 3,500 before I brake. Quite a different concept from my old 7.3 Ford that operated down in the 2,000 RPMs.

Now quit playing with that computer and keep your eyes on the road! [IMAGE]http://www.emotihost.com/glass/15.gif[/IMAGE] hahahahha

Bruce Lenhardt · 05-01-2007, 02:15 PM

I do the same thing-I don't like for the RPM to get high and stay there, so I give it stiff brake to get em down. On my 6.0 on the interstate, I was getting about the same MPG-around 18 to 19.

Emmel · 05-01-2007, 04:37 PM

Not too sure of the Ford, but the GM in tow/haul you have to watch the brakes. If you stay on them too long it will downshift tranny to a lower gear and the revs go thru the roof!
Now for the onboard computer, check your gas consumption from point a to point b and devide the amount of fuel used to travel that distance. That will give you the correct MPG! My Monte Carlo has an onboard computer and at 65mph on level ground it says we get 35mpg, yeah, I wish! Use the true calculation with the real numbers.

sailer · 05-01-2007, 04:44 PM

if you think you get 19 on the level try going down hill with nothing behind you and now get 65 mpg but who is kidding who ,, as they say the fish is how long ,, now get real and forget the mpg and start having fun and enjoy life

bsmeaton · 05-01-2007, 05:29 PM

Seems to be some confusion over instant MPG settings and average MPG settings on the computer.

Instant MPG gives you real time fuel consumption based on the last few seconds of engine performance. On a fuel injected engine going down a good hill, this reading will be maximum MPG the computer can read (99 MPG on mine) as the fuel system is not providing any fuel at all. Uphill this can drop to as low as 3-4 MPG, depending on the load and engine.

Average MPG is the average fuel consumption since the last time you reset the computer, regardless of how many miles you have driven or fillups.

I've checked mine longhand - and the computer is very close. Just make sure you reset the computer when you want to get an overall average for a specific trip or distance, otherwise you are bringing in the average for the last few weeks, or even months, since the last time reset.

daneboy · 05-01-2007, 06:04 PM

David,
The Fords automativ down shift tranmission works great at keep you slowed down. I agree with Brad, let it run up to 3500 and apply some brake. My 06 PSD has 30K and is getting around 10.2 mpg towing @ 65-70 mph, solo 17 mpg @ 75-80 mph.
Enjoy,
Jerry

rldriver · 05-01-2007, 07:08 PM

David, our Dodge uses about the same amount of fuel as your Ford. On our last 300 mile trip with out the Big Sky we averaged about 21 mpg, wow, I thought that was great. Towing the Big Sky from the dealer (50 miles) my computer said we averaged just under 10 mpg. Looks like I will be pulling it about 300 miles in June so will check it out then.

Fordzilla · 05-01-2007, 09:47 PM

Mine gets 15-16 driving flat roads solo, and 11-12 pulling the Monty at interstate speeds. I would bet I could get 12-13 towing if I slowed down a bit. I have never taken a longer trip with the trailer in tow where I could stay on two lane roads and tool along at 55-60mph though so I have no proof. I have 25k on the diesel so it's getting broke in well and I have the 4:10 gears which help towing but hurt solo mileage.

richfaa · 05-02-2007, 03:21 AM

David..Were you in tow haul mode cruse control engaged.I have found that the TH and C/T sort of interfere with one another.The cruse tries to keep the truck at the set speed and the TH tries to find the right gear ..That results in some high RPM's. I like to control the RPM myself instead of allowing the C/T to do it for me. I always use the TH mode but do not use the cruse in very hilly terrain. The TH does act like a Jake brake and will pretty much maintain downhill speed without excessive braking. Experiment a bit with the C/T engaged vs not engaged. By the way the proper way to apply brakes going down hill is called "stab braking)
Ex; Say you wnat to maintain 50MPH downhill. you let the speed climb to 55mph, Stab the brakes till you decrease to 50mph..let it increase again, then repeat...(that is part of the CDL test) In order to get a good average MPG reading you must let it go for a long time. I can reset it on a nice level of road and get 16MPg over 20 miles..then hit some serious hills re set it and we are doing 7MPG. Set it and forget it, check it at each re fuel.

bsmeaton · 05-02-2007, 09:21 AM

Rich,

Whats the upper RPM range on your gasser? Does it have a "redline" on the tach? Just curious what those wrap up to these days.

richfaa · 05-02-2007, 04:21 PM

The high end of the tach reads 8000RPM..there is no "redline"..I would not want to hear what that sounds like...

bsmeaton · 05-02-2007, 04:36 PM

Wow, thanks rich. These high tech engines are really something.

Cat320 · 05-04-2007, 02:46 PM

One thing I really like about the D/A...and all diesels, it runs the same rpm whether pulling the Montana or empty. In the T/H mode, the shift points change, but other than that all's the same.

happy campers · 05-05-2007, 03:25 AM

Quote:

quote:Originally posted by Cat320

One thing I really like about the D/A...and all diesels, it runs the same rpm whether pulling the Montana or empty. In the T/H mode, the shift points change, but other than that all's the same.

It just uses more fuel to keep it there!

ggranch · 05-05-2007, 04:33 AM

Took the first pull with T/H Wed, returned yesterday. Finally, I have a Tranny that thinks like I do. Loved it! With less than 1K on the clock, I'm not even going to look at MPGs. Alot of good suggestions in this thread!

gj4040 · 05-07-2007, 02:40 PM

The above is correct about the only thing changed in the tow/haul mode is the shift points to better handle the increased load of the 5th wheel. The Ford manual even states that all the gears, including overdrive may be used , even in tow/haul mode. It makes no sense not to use the tow/haul feature when pulling a heavy load because that is what it is designed for.

Wrenchtraveller · 05-07-2007, 07:08 PM

My V10 shifts at 5200 if you keep your pedal to the carpet but with T/H, I can see 4500 RPMs going downhill as the Torqushift downshifts to help slow the trailer down. Most grades I can pull at the speed limit at around 3500 RPM. I pulled with diesels for 12 years and the new 3 valve gas V10 is not too shabby at all. We are heading west tomorrow after 3 weeks in northern Alberta and so far the Montana and truck have been great.

tcorbitt · 05-08-2007, 12:16 AM

Hi Dave,
Your numbers and experience with Tow Haul as others have noted are consistent with our 06 Ford PSD.

Tim

richfaa · 05-08-2007, 03:43 AM

I agree with Don on the V-10 pulling most any grade at around 3500RPm at speed limit which may be 45/50 MPH. The best grade we did on our trip was 9 1/2 %, speed limit 50MPH and we topped at 50.3.. The V-10 is certainly not the diesel but it is very impressive. I think we only hit above 5K rpm's once by accident...don't like that sound and that is why we do not use the Cruise on very steep grades. Still waiting for the 08 rebates to surface.. In this area(Ford Country) Ford is closing a Casting plant and shutting down a engine plant for one year..the7 are in big trouble and we expect to see big rebates on the SD..Of course..who will be left to afford one???

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