IDK to me the 5.5 mpg does not sound crazy, I've gotten as low as 6 mpg in daily driving my empty Ex. Towing I keep my speed and put it to the floor and let the truck do the work at whatever RPM/Gear that may be. Plenty of time has been spent at 4,500 rpm in 2nd but holding 65+ up large hills in the mountains.

 

A HA! I don't know why I didn't think of that. Defiantly 3.73's! So seeing that a definite gear change is in order, what ratio do you suggest? I'll be staying with stock tires and probably be towing at least the weight I tow now. The primary function of my X is my mule so it's on permanent tow duty. I tried to keep my speed at 70 because of the time constraints I had, which meant several shifts to 2nd at about 4500 rpm-ish. I do realize that'll usually drop the MPG's dramatically but again, I was on some pretty tough time constraints. Once I go on my short tour, I'll be able to order a lot of parts for the gear swap and probably the tuner from 5 star as well. As soon as I get home from my short tour, I'll be moving so in a perfect world, I'll have everything waiting for me when I get home, be able to knock it all out (at least the rear gears and have all the stuff to do the front) beak in the gears, change the fluid/make adjustments if needed, and hook up and go. We'll see how that all plays out though.

Awesome! Thank you! Yeah I agree, the 2522 is a little closer to 2600 but it pretty much justifies the 3.73's.

Yeah I see what you're saying, I was concerned that there may have been something wrong with my X because I've seen a lot of people say they get 8-9 towing more weight. Now if I can make some tweaks to give my X more power and better MPG's, I'm probably gonna go for it.

 

On my stock size wheels and tires, I am just under 2200 @ 65 MPH in OD. When I had 3.73 gears it was a bit under 1900. If you are around 2000-2100 then you would have 4.10 gears.

4.10 came on pickup trucks and 5.4 EX rigs, but as far as I know it was not an option for a V10 EX. Perhaps the PO got a rear axle cheap from a truck with 4.10 ratio and then changed the front to match. That would explain the tags. Changing to 4.30 gears from 3.73 didn't change my towing mileage, just made the drive-ability much better.

Regardless, that doesn't explain your poor mileage. A good part of that is staying in 3rd gear drinks more fuel. But you should have been able to stay in OD on the level spots. Seems like you are down on power. An 8000 lb trailer should not be too much for your truck, especially with an aero nose on the trailer which definitely helps. Towing my flat fronted brick that weighs 7000 lbs, I never get less than 8, and usually 9+. That includes travel all over Wyoming with it.

Have you checked for codes? Does it seem to run properly, smooth in all gears etc? Possible intermittent misfire? I'd also change the PCV valve, cheap and easy.

 

That 6 MPG is in the dead of Alaska winter locked in 4WD and hours of idling per tank.

5.5 on the highway towing what the OP has for a trailer tells me something is fishy. So does not being able to hold OD on level ground.

When I had 3.73 gears, I could hold OD @ 65-70 on flat ground towing with no problem. It wanted to hunt gears @ 55-60.

 

I'm glad Alaskan X saw this thread, I was going to tell you about him AND HIS PLATES. They read 8MPG That's his hand calculated daily driver average !!
You have totally lost me in your eureka moment BUT I will say this: If your rear tag reads 4:10 & the front reads 3:73 you dang better really find out what's you got in them pumpkin's

 

Fwiw the 3.73 axles i have seen have a bunch of codes on the tags. One of which on mine say "4.10" however I have 3.73 and its never been changed. I believe there are other codes on that tag that will tell you the gears.

 

You do have me there, but it is empty commuting

With my trailer and truck loaded, lets say it's 5,500 in weight (need to scale it) I know my 3.73 truck can hold O/D on flat ground, but any sort of incline and i'm back in 3rd. This is with a 5-star tune and at 30ft-1,500ft above sea level, not close to the elevation and weight he is seeing. I'm just thinking it's not that far off what I see in my conditions. Now what I will say is I am able to get 8 MPG towing my trailer at 5+ the speed limit in the mountains, that is the same MPG i get commuting back and forth to work in the summer with no idling and no 4x4/locked hubs....it just doesnt seem so far fetched to me considering the conditions from what we are being told...that's all

 

I think your going to be surprised to find out that the little trailer you have only weighs about 550lbs with 2 feet of snow on top

 

In 3rd, I'm at about 2600rpm at 60 mph, about 2200 in 3rd at 50mph. In OD, I was at about 1800 rpm at 60 and about 1550 rpm at 50mph. Yeah I'll probably change the PCV valve also while I'm here.

Yeah the 5.5mpg was constantly moving and quite a few grades around 4500 rpm. most of this was at elevations on 3000-5000ft above sea level and a lot of decently steep grades of 5-7% IIRC for a cpl mins at a time at least. I know altitude can result in power loss but I thought what I experienced was a bit much. It wouldn't go into OD at all unless i was going downhill. As soon as the road became level again, it would go to 3rd.

my Eureka moment was that I put a mark on the tire and the rear driveshaft and counted how many rotations the drive shaft turned to 1 rotation of the tire. 3 3/4 rotations of the drive shaft to 1 tire rotation told me that it has 3.73's. We tested 4wd before we bought it so I know both axles have the same ratios. I agree if they didn't, that'd be ugly for sure!

 

If the unloaded drivability of your EX seems healthy with no codes and smooth running and shifting I think the mixture of load, terrain, altitude and speed all add up to the end result of that 5.5 MPG run. Pulling a little heavier trailer at slightly lower speeds (60 to 65) on flatter terrain at lower elevations I saw as low as 6.5 MPG. Seems legit to me. With the exception of the weight every other aspect of Repo's trip conditions compared to mine will result in a decrease in MPGs. I use an Ultra-Gauge UltraGauge OBDII Scan tool & Information Center to monitor the instant MPGs (along with several other parameters) and when it is in 3rd vs OD the instant MPGs drop considerably depending on load, speed, etc. I attribute the better MPGs I am seeing mainly to staying in OD more. Gears move the RPMs up into a better power output range, the headers help to make a bit more power (even better at those higher revs) and whatever extra umph the tunes offer add to the mix (along with much better trans strategies) of increased power output that allows the truck to hold onto OD under higher loads. The more time spent in OD, the better the trip MPGs will be. Any change you can make to the truck to move in this direction will be a plus as well as any changes to the trip conditions that allow for more OD time.
If this EX is to be a more or less dedicated tow rig (less of a daily driver) then I would recommend 4.56 gears with stock sized (or 285.75R16E) rubber. This change alone will deliver a much improved towing experience for you. If it is going to do of a mix of towing and DD duties then 4.30 gears may be a better choice for the slightly better MPG potential while unloaded.
I would also suggest getting some sort of tool to display the instant (and trip) MPGs to monitor during tow trips, it's interesting to see how throttle openings can be reduced a few percent to boost MPGs while maintaining the same speed at times.

 

Unloaded drivability seems fine. It runs nice and smooth except when I have the a/c on. When the a/c's are on, it seems like there is slight I don't want to say miss because it's not even that pronounced. Not sure if that is normal for the v10's or not now that I think about it. With a/'s off though, it's super smooth. Again, with the a/c's on, what I'm talking about isn't that noticeable at all. And it's only at idle, nothing noted at any other rpm range, super smooth no matter what. 4.56's sound better based on what you described because the X won't be a DD, just a mule. That Ultragauge looks pretty cool. I'll definatly look a that. Are you able access the trans temp on yours? It said in the site that it's possible to access it so i was just wondering. I haven't had a chance to pull codes yet, maybe this weekend.

 

My UG is a previous model to the current version but I don't think they ever included the Ford trans temp PID to their software. They had promised it in a future release, then that came and went (twice I think) without it happening. I use a stand alone GlowShift MaxTow gauge to watch the trans temps. GlowShift | MaxTow Double Vision Trans Temp Gauge with Electronic Temperature Sensor There are some great apps that work with phones and tablets using Bluetooth dongles that read all of the OBD outputs if you want to go that way.

 

Cool, thanks. Is that slight roughness that I mentioned with the a/c's on normal for the X's?

 

No that's not normal

 

I agree, not normal.