I have 3,600 miles on my F350 6.4L SRW w/3.73 rear end. I made my first towing trip with it over this past weekend. I averaged 7.3 mpg towing 14,800 lbs. for 300 miles with quartering moderate winds at speeds generally between 60 and 65 mph over mixed terrain from flat to moderately hilly.

I talked to a guy next to me in the campground who drove about the same route pulling 16,900 lbs. with a 2006 F350 6.0L w/4.10 rear end who told me he averaged 12 mpg driving 65 to 70. He seemed like an honest guy who wasn't lying.

Even if my truck improves as much as 20% with more break-in, I still would not be at 9mpg. Therefore, it looks like this 6.4L might turn out to be a real fuel hog. Sucks for me!

 

Like I've mentioned many times around the forum, our F450 4x4 ambulance at work started out getting 5.6MPG and at almost 6000 miles and over 600 hours later-is still getting 5.6 at best.

Mike

 

Man thats terrible..... This is my only real gripe with the 6.4. Supposedly theres a new flash out that is suppose to help mpg some, I would definatly go try and get it.

 

The 6.4 seems to be capable of delivering 15 mpg and up, but you will not see the same mpgs as the older diesels trucks that were lighter, and had less emission controls.

mpgs will improve as the engine wears in, but you won't see the same mpgs that some folks associate with diesels. Besides, these engines were built for power, not so much economy.

Although, I am at a loss as to how its even possible for a diesel of that size to only get 5-6 mpg. If my 6.9 did that, there would probably be a black smoke cloud to cover the whole west coast (13mpg is what I get if I drive like I stole it on the freeway).

 

Let me tell you this, the last update FORD offered middle of Aug to help with other common issues including this one made zero diffrece as for increase in gas mileage. As soon as I got word of the re-flash I was at the dealer having them flash my truck. Here we are 1,500 miles later and i'm still seeing the same gas mileage number...... 12.4mpg/7,600 miles


Nick

 

I would suspect the '06 with the 6.0L PSD and 4.10 gearing might get better fuel mileage because of the gears. When unloaded...the gears do not help MPG's, but when towing...boy that is when they shine.

7.3mpg is still pretty low, but after reading some of the mpg's on the 6.4L PSD...one thing that seems to help is the FORD fuel additive. IMHO...it should not be necessary, but then again...it does appear to help. Maybe while towing...it might be advisable to use. Seems to cut the regen cycles down also...which will help mpg.

Good luck...


biz

 

Adding an aftermarket overdrive was popular back in the late 80s before overdrive transmissions were common place in HD pickups, if its possible to add a unit like say, the gearvendors overdrive, it would go a long way to compensating for the big gears that the new superduties have.

I suspect its only a matter of time before we see these units making a comeback on the big fords.

 

Thanks much you guys for your replies. As you might guess, I'm feeling pretty damn bad and quite stupid for dropping 45 grand on this 6.4L when anyone with good sense would have waited a year to find out how it really performed instead of listening to Ford's hyper-hype.

I like the idea of someone coming up with a flash to improve the 6.4L fuel mileage and I would buy it in a heartbeat. How would I know when something like this became available???

I'll definitely try the Ford fuel additive and let you know if it helps. It would be a good thing if we could keep this thread going so we could continue to report on this whole low fuel mileage issue with the 6.4L. How can we do that?

Does anyone know if it is possible/practical to switch the rear end from 3.73 to 4.10??

How can we reach a larger and larger audience with this issue until maybe, just maybe, we get Ford's attention? That is, if they even give a rat's patoot about it.
Best,
T-Trash

 

Been doing the mixture of driving I normally do, about 50% highway & 50% city. 12.6 mpg, this hasn't changed for about 5000 miles. If I do a highway only drive, and keep it just under 2000 rpm, I will get 18 mpg.

Towing a 21 ft. boat knocks these numbers way down.

 

I have a 08, F350, 6.4 and pull approximately 10,000 lbs. My overall mileage while towing (60-65 mph) is 9.8 to 11.5 depending on the terrain.............I have noticed, that if I tow in overdrive, my mileage reduces drastically because of constantly giving it more accelerator in order to maintain my speed. The mileage mentioned above is in the "tow" mode.

My son also has a F-350 with considerably more mileage, tows about the same weight, and he consistently runs in the 12-13 miles a gallon range in the "tow" mode.

This is such a safe truck, I can put up with the lack of gas mileage. I had to do a sudden (interstate) stop over the weekend, and the truck/trailer handled it very very well!

 

Some of my friends that I have met at campgrounds in the past have said they got 18 mty and 12 towing. Talk can be cheap sometimes even by the nicest guys. For some reason it seems to be human nature to exagerate. Yes at some points they can get that type of milage. One easy trip mty to Maine and back 400 miles I got 16.8 on my computer Once part time towing I got 12mpg. It would be easy to brag and say I got that all the time. For the guys that write down their milage and keep logs it may look like My 450 for the 1st 2,000 miles averaged 11.7 hand calc. towing about 17k 8.726 for 2,000 miles. Now that I am broken in,last tank was 13.46 rural and some city. computer showed 14.3(sure was off). Do not expect quite this good but would be happy with 12.5 or so mty. Yes lighter trucks with 3.73 gears traveling slower nonstop can get higher milage. Also did you scale out. I use to think I was towing 13,500 when I scaled this year found out my gross was 16,650# over the dry weight of my truck 8,700# giving a total of 25,350. Found it only downshifted on steeper hills in the Poconos. You might have spent a little more time in drive than OD.

 

Can the TS transmission be taken out of OD? My 05 V10 TS has the tow/haul but no way to take it out of OD except with the throttle. Or do you have a manual transmission?

 

My 08 has a tow/haul selector on the end of the transmission shifter. I leave it in that mode when I am towing and still run through all the gears. If I deselect it and go into OD, I find I must use more accelerator to maintain my speed, plus I don't have the down hill braking that the engine seems to give me in the tow/haul mode. My RPMs or turbo readings do not change from one to the other, but going up even a slight grade, the transmission will start looking for gears in OD. So, I think driving in OD while towing is probably a wash.

I do not understand exactly how the transmission works, but even though you run through all of the gears, it feels more responsive and powerful in the Haul/Tow mode as opposed to OD.

 

I believe 1 of the features of tow/haul is that it firms up the shifts, which is why it may feel more responsive and powerful.

 

I found it delays the shift by letting it go to a higher rpm such as taking off loaded it might shift at 2200 rpms in none tow mode but tow mode will hold it to about 2600 rpms. Found when I am going down hills mty I just pop it in tow mode to let it downshift to slow it down with out using the brakes so much too.