Ford 6.0 PSD towing my cardinal--best mileage speed?

markj · Post by **markj** » Fri Apr 18, 2008 9:18 am

My truck shifts into overdrive at 61 mph while in tow/haul mode. The engine is obviously running slower, but working harder. I'm wondering if anyone else with my configuration has tested fuel mileage while running on a flat road in overdrive at around 61 mph, vs. underdrive at say 55 mph--where the engine is running faster, but working easier. I'm thinking it can't be all that different?

campswithcritters · Post by **campswithcritters** » Fri Apr 18, 2008 9:33 am

Mine shifts at 61 or 62, I have found slightly better at 55 but not much. I attribute most of that to reduced wind resistance.

Rob & Cathy · Post by **Rob & Cathy** » Fri Apr 18, 2008 10:54 am

Hi Mark, I agree with Bruce, the biggest factor is trying to move that big sail down the road. But who wants to drive at 55?

Rob

Post by **Mike Clay** » Fri Apr 18, 2008 5:13 pm

Well i dont own a furd but my truck is best kept under 65 mph

CritterRenter · Post by **CritterRenter** » Fri Apr 18, 2008 6:02 pm

Mike Clay wrote:Well i dont own a furd but my truck is best kept under 65 mph

Mine seems to run best just under 65 too, mileage, EGT, and performance. If running at 55, I do better out of overdrive.

Rob & Cathy · Post by **Rob & Cathy** » Fri Apr 18, 2008 7:18 pm

CritterRenter wrote:
Mike Clay wrote:Well i dont own a furd but my truck is best kept under 65 mph
Mine seems to run best just under 65 too, mileage, EGT, and performance. If running at 55, I do better out of overdrive.

Tow/haul mode in the Fords with Torque Shift transmissions, an I believe GM with Allison, chances the characteristics of the transmission. When you're towing you definitely want to stay in tow/haul mode.

Rob

campswithcritters · Post by **campswithcritters** » Fri Apr 18, 2008 11:35 pm

Rob & Cathy wrote:Hi Mark, I agree with Bruce, the biggest factor is trying to move that big sail down the road. But who wants to drive at 55?

Rob

Don't want to but there are a couple of states (CA & IL included) that limit trailer towing folks. I also do a LOT of backroads driving and many of those are posted 55 and better driven at those speeds. Sometimes its actually a pleasure to slow it down and enjoy the veiw!

Don't worry about Ernie dropping it out of overdrive, he has a 6 speed manual.

Post by **Don Wilson** » Sat Apr 19, 2008 4:57 am

The California speed limit of 55 towing a trailer is very rarely enforced!
I had a CHP pull beside me when I was doing 65 and flash five fingers at me twice and that has been it.

If you do 55 in California you will have the slow lane all to yourself as the only truckers that drive the limit are the ones who have so many points they are about to loose their license or their truck is in such bad shape it will only get up to 55!

Don

Rob & Cathy · Post by **Rob & Cathy** » Sat Apr 19, 2008 6:08 am

campswithcritters wrote:Sometimes its actually a pleasure to slow it down and enjoy the veiw!

True, true, but that's why they invented back roads.

Rob

Rob & Cathy · Post by **Rob & Cathy** » Sat Apr 19, 2008 6:13 am

Mike Clay wrote:Way to go Ernie another oars man, yes Bruce Calif is one of those states 55 mph while towing. Its great except with the 6 speed i am almost right in between gears (5th & 6th) kind of with i had 5th 1/2.

Manual shifting??? I thought that went out with sticking our arm out the window to signal a turn.

Just kidding Mike, just kidding.

Rob

Post by **Mike Clay** » Sat Apr 19, 2008 6:31 am

You mean you dont have to stick your arm out the window anymore to signal for a turn

Dont worry Rob some day I will be auto impaired again

Diesel Dave 04 · Post by **Diesel Dave 04** » Sat Apr 19, 2008 7:30 am

I got 10.5 MPG draging My sail down the road running 62-65 MPH But I have 4:10 gears Not 3:73 and I get OD a little sooner, and btw That was my best towing MPG if i run 70-75 i drop to 9-9.5 MPG.

CritterRenter · Post by **CritterRenter** » Sat Apr 19, 2008 4:28 pm

campswithcritters wrote:
Don't worry about Ernie dropping it out of overdrive, he has a 6 speed manual.

I have all the gears I want now. A 6 speed stick is cool

Just a habit though, I still stick my arm out for a turn.

Old "Fogy" I guess.

bigbunkhouse · Post by **bigbunkhouse** » Sat Apr 19, 2008 6:52 pm

Not to hijack with non diesel talk but with my F250 gasser I have 4.10 gears and 35 in tires! This moved the power to speed ratio a bit... so If i'm running under 60mph I get better mileage in 1:1 (3rd in my case) than in OD. The diff is I get 14 +/- in drive and drop to 12.5 +/- in OD, my educated guess.... The peak torque is just about the RPM of 55 in drive and with the little 5.4 L it struggles to push the ladder racked, lifted, big tired, tool boxed,visored, plow framed, tool filled 7400lb, 200k mile beast in OD at low rpms.

My 79 with a 450 hp 460 with 600 ft/lbs would tow a t-14 bobcat trailer at 23k combined at 1500 rpm and get 10mpg but when empty no matter how I drove i'd get 10mpg also.

Todays moral ..... GOT TORQUE?......

I'd like to hear what you diesel guys find for a diff in mpg in and outa overdrive at the same speed, see'in as where ya'll have goo gabs of torque all thru the rmp range!

If nothing else, if staying in drive keeps your tranny from shifting you are saving huge money buy not frying your tranny. My 250 has 200k on the original tranny thanks to not using OD and having the tranny hunt all day.

I know I ramble, but i'm getting help!

CritterRenter · Post by **CritterRenter** » Sun Apr 20, 2008 1:21 pm

Mike Clay wrote: Its great except with the 6 speed i am almost right in between gears (5th & 6th) kind of with i had 5th 1/2.

I had a Gear Vendors Aux. OD gearbox on my old '02. It was great, gave me that 1/2 gear that I would like to have now. I had a problem with it, and GV backed up their product 100%. Had a replacement G/B the next business day. They even helped me with warranty issues when the local dealer misdiagnosed the problem. I ended up with an overhauled factory tranny, reimbursed, and a new aux. OD.
I would like to get another, but so close to retirement, I'm saving money...