I have a 2015 F-350. I bought it used with 15000 miles on it. I was getting 17 to 19 mpg. I hauled a large load with it 800 miles & was getting 12 to 14 mpg...understood. Now I have been driving it for almost 2000 miles since I had the large load and can't get over 14 mpg. I drive 15 miles to work everyday that is all highway. Does anyone know what could be wrong? It is under warranty and I took it in & they changed the fuel filter which only gave it another half mpg. They don't know what's wrong....Really frustrated.

 

reset the mileage indicator?


Try to hand calculate it going forward.

 

Diesels don't get good mileage till totally warmed up. 15 miles even on the highway is just about getting it to the heat saturation point. Remember, they have no spark plugs and rely on heat and compression for combustion and economy.

 

Welcome to FTE. I don't know where you are located by outside temperature has an impact, as does winter blend fuel. All depends on where you live. Doesn't sound like anything is wrong, to me.

Bruce...

 

Thanks for your responses...

I have been hand calculating it before, during and after I had that load on it. The temperature was the same during that time frame and only in the last week has the outside temperature go down below 60 degrees. When I was getting 17-19 mpg back in August, I was still driving only 15 miles to & from work.

I have also heard, that Ford has something in their newer engines that "learn" your driving habits and thought that maybe that feature didn't "relearn" after I was no longer pulling a load. They said it may need to be reset but the Ford dealer service department says they don't know how to do that....is there any truth to this?

 

I've heard that the tranny has a learning curve, can't confirm it, but not the engine. ECM looks at all the parameters and where your right foot is and that's about it.

 

I'm not an Expert:

But there are certain modules that do learning. For example the Transmission module (TCM) changes shift points. I have monitored certain PIDs and noticed different MPG after my wife driving or pulling my trailer. I get lower MPG because I have a heavy foot. If I drive erratic and then drive smart like my wife, I can see that the fuel rate stays high and turbo haven't spooled down at idle especting me to tramp the throttle for some time.

When you get work done on some componets the dealer will say that the module will have to learn your habits.

 

you can take the cables off of both batteries and that should reset the relearn process. Leave them off long enough to discharge the system.


turning on the headlights should do the trick.

 

Welcome to my world. That 14-15 unloaded for that type of driving is what I get. Now when you throw in colder weather and winter fuel, it goes down from there for ME. LONG highway drives I can pull 17-18. Highway sections at 45 mph I've seen 20... But 20 doesn't last that long.

You could also be stuck in a regen loop. 15 miles is about enough to get the truck up to temps enough to start a regen, burn some soot off, but then you shut it off and a couple of your 15 mile trips later, it has to start all over again. That happened to me and because my drives were shorter there was a stretch where I was getting 10 mpg unloaded.

Assuming you have a Lariat or above trim (or the 4" screen on a XLT) You can add a DPF % screen to the dash to find out. The dealer can do it, yes, they usually charge for it. Or if you have an ELM OBD2 device and a laptop with Windows, you can use a free program called Forscan to add it. There is a long thread on how to do it and of course a lot of people here can help you with that if that is the route you want to go.

 

No expert here either, it must be the way we drive our vehicle. I put my plow on today we're expecting up to 6 inches of snow thank God it won't last long, however as I was driving around today I couldn't help but laugh watching the truck pull 16 mpg driving around with all that weight .

Fisher Xtreme V 2 that weighs 1044 pounds
my regular Tools in my toolbox 450 pounds
600 pounds of tube sand for ballast
And about 40 gallons of diesel fuel in the transfer tank about 284 pounds
then of course the transfer tank itself fuel pump lights and all the other crap I have on that truck it's just funny too me to hear people can't get 15 empty. Now I know what sticklers for numbers so before I went to work this morning I filled up and drove to my job and then drove home today 55.7 miles fill the truck up 3.45 gallons the total MPG was 16.14 somewhere around there don't know what to tell you totally believe you just don't understand how I can't see 15 even with the weight I am hauling. Now it will be interesting to see first time I'll be plowing with this truck hopefully it's wet heavy snow we'll see not sure what the numbers will be take care

 

I know what a lot of my problem is, and it is idle time. I idle a lot. I picked up a 1 mpg by turning the truck off when I wait to pick my kids up at school. I don't remote start anymore either. Plus, having the truck in the heated garage helps a bunch as well. Winter fuel and cold temps and I still pulling 14-15 mpg for my daily driving needs.

Second issue is that I don't drive that far and there are a few lights that are a pain - you don't get MPG sitting at stop light.

I think you are going to be very happy as I noticed that weight doesn't effect the mpg in a diesel nearly as much as a gasser. I get that 17-18 on the highways here with a full tank (38 gal), an extra 30 gallon in jerry cans in the back, 700-800 lbs of people, our gear, two coolers filled with ice, drinks, and food... I always keep my tanks and cans filled up as a long drive here means a long drive without services. Maybe 1500 - 1800 pounds of stuff. (I carry tools, oil, extra DEF, distilled water, a case or two of water as well)

The 2011 I had, I got 23 mpg for a section of highway I drove at 45 - 50 mph steady. No stops. I even hand checked at the next fill up to make sure the computer was right and it was. It just isn't my normal use case.

Radium - I am sure part of your awesome MPG is that you always get a good, complete regen cycle in. I almost never do...

We just did our 6" - 12" snow... Melting this weekend and supposed to rain. I Hope the ice melts before the rain.

 

The only learning that goes on is the pressure shift point for your particilar transmission. It has zero to do with you or your personal driving habits .

Yes a new fuel filter can help mpg, but only if it was plugged. Pull your air filter apart and look at it. IT should be fine at 30 k+ miles unless you or your predecessor live in a very dusty / dirt road environment.

If your fueling stops switched to a higher bio-diesel content, your mpg will go down. however, the price should go down too, but that does not always happen. Yes winter fuel too, but, unless in Alaska or northern Canada, a bit early for that unless folks are cheating.

Unless temps are in the 90's, switching from 5-40 or 10-30 to 15-40 oil can make a really big difference on runs less than 200 miles.

regens happen on a regular frequency, and if you get off cycle, it can be the pits. If you have screen display, watch for when your instant mph is below 10 mpg unless coasting - that means you are in regen. lock out 6th gear at highway speeds. lock out 5th if city driving. this keeps rpm's up during regen and results in regens getting you down to dpf being only 5-10% filled. If you do not lock out those gears, you only get down to 45% filled. this affects the mpg until next regen, which will happen much sooner if you only get down to 45.

remember, you weigh 8-10,000 pounds, with a front that is not aerodynamic. the slightest wind can make a big difference. colder air is denser and thus makes a big difference. not using the air conditioner on recirculation can make a big difference- but on long drives, you need to switch to fresh or open a window if you don't want to get sleepy.
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15-40 oil Does affect my Fuel Mileage. Noticed at my last oil change by the dealer and took it right back to them and had them change it back to the 10-30. New Service manager thought all the diesel trucks took the same oil. I explained it and then He looked it up.

Next month the local fuel stations should start to switch over to the winter blend around here. Fuel Mileage will suffer again.