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2015 350 XLT with 3.7 L/3.73 rear.. horrible mileage

13300 Views 27 Replies 14 Participants Last post by  ranxerox
First of all, we do live in WV so there are some hills around here, so I expect *some* decrease from the 19 mpg highway estimate. However, I'm getting a hand-calculated 13.7-14.2 around here most of the time with an 80/20 split of highway/city, respectively.

Van has 35,500 miles on it and the only thing that's not stock is the tires... currently running 225/75/16's instead of the 235/65/16's, so it's a 4% increase in tire size... that only equates to around 85 rpm at 70 mph, so it's not much. I had to change them out after we'd had the van less than 2 weeks because the stock tires started showing cords and throwing chunks of rubber off of them at 34,500 miles.

Anyway, I talked to a guy from church today who has basically the exact same van as us with the same amount of people to haul (and drives the same route to get home), and he's getting 17-17.5 average, so around 20% better mileage. I have no idea what's going on with this thing.. There's no CEL showing, so it doesn't appear to be something so big the computer is fussing about it, but I can't imagine that mileage being anywhere near normal. If I keep it at 45 mph around here on the side-roads I can get a decent mileage reading on it if I reset it and run a few miles, but once we hit the highways and actually have to GO anywhere, the mileage drops like a rock. I don't ever even push it past 72 or so, either, so it's not like I'm running it hard.

Any ideas? Going to try to get it into the dealer to run a diagnostics on it for the awful mileage this week, so hopefully that will shed some light on it. I'm just about ready to trade the frustrating thing in for an ecoboosted van, though, as at least those have a decent amount of torque to get up the hills.
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I can understand a drop in fuel economy with AC running with city driving. But highway MPG driving should not really be effected by the AC. It should be a marginal difference, or negligible. But yah in the city idling around it would be a different story.

I certainly had slightly better expectations for fuel economy than I see. My 5.0 V8 F150 4x4 wasn't worse, seems about the same. In fact I think the v8 was better on the highway. And my F150 was a super crew long bed, 4x4.

I think I'd actually like to see them put the v8 5.0 into the transit van. I actually would have to try driving that and would consider it over the EB.
What tire pressures are you running? I'd also check the air filter and make sure it's not moist. I don't remember whose post it was but I recall an MPG drop with a soggy filter.

It seems to me you may have several small things contributing. I love the usage of "attacking" those hills, lol.

Yeah this AC seems like it has to work pretty hard. I've heard of a dropoff in mileage due to AC but it's kinda ridiculous. Probably due to a lack of insulation?

I think I'm running 55 in the fronts and 70 in the rears. Air filter was just changed at the dealer two weeks ago asking with the rest of the parts for the water issues recall. It just seems really strange that the van if so gutless up the hills. WV hills aren't the Rockies and this thing shouldn't be having THAT much trouble with them.

Fwiw, the service tech said he couldn't do anything about the mileage unless I has a cel showing, which there's not.
Yes good luck getting Ford to do anything about poor mileage. My dealer spent some time with Fords hotline in regards to my vans MPG (10-12), and was told it could be due to roof rack (factory rack) and or my conversion, (800 pounds), and are not willing to do anything unless a code shows up, they referred dealer to owners manual in regards to fuel economy and driving tips.

I have been to dealer now 11 times since I bought this van with various issues, and have discovered that Ford does not care about you at all once you gave them your money for your purchase, 10-12 MPG is normal? Ecoboost my ass there is NOTHING ECO about that.

10 mpg under a diesel is a lot of $$ going out of the window
I have a 2016 transit 250 with 34700 miles. I average between 13 and 14 mpg. It’s a 3.7. I don’t like the mileage and whenever I hear other people getting between 17 and 18, I also have to wonder why. We’re you ever able to do something to change your mpg ? I drive hilly country as well.
Check your air filter to see if is wet. Then read the long thread on this fourm regarding this issue.
since this is a mileage thread, I wanted to say that if you really want a good way to check your mileage, download the free "fuelly" app and use it to enter cost/gallons/mileage every time you get gas. its easy to use and I do it while the pump is filling. It makes it really easy to "hand track" the mileage so you know its correct. I also track oil changes and other maintenance in it as well.

and click on the mpg in my sig to see my fillups and mpg over time.
I didn't have a noticeable mpg drop in my Sprinter when using AC, both front and rear. And I don't notice a difference in my Transit, either. If there is any, it's less than 1mpg. I get the same mpg in 100 degree weather with AC on as I do in the winter with the heater on. Or when I have neither on. AC is either on or off, there is no gradient. Fan speed DOES have different settings, though. I suspect running the fan at it's highest setting uses less energy (alternator drag) than turning on the headlights.
The only thing I've noticed that gets me better or worse mpg is how much weight I have in the van.

At 49k I'm at 15.3 average mpg. Some highway trips have been 17-18mpg on a tank.
Keep it under 65 MPH and you will get great mileage for a 2 ton truck!

Incomplete info but it proves the point.
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