Has any one had the experience where under the same or like conditions you instant fuel mileage will change as much as 10MPG ?

I ask this because I have had this happen to me, driving with the cruise control on I have had it start out at 11.7 MPG and after 20 miles at that it will jump to 21MPG.
It almost sounds like a computer issue, my sync has not worked right since the purchase of the truck as well, are they related?
I drive a 13, 6.7, 250 .

Any suggestions? Tech services can you help?

 

11.7 in cruise control sounds like you were in active regen. Also, if you reset the meter and had some stop and go driving or idle time prior to reaching the highway, 11.7 is very likely and then the highway mileage overcame that over the 20 miles. Is it possible that you accidentally reset it while you were cruising?

 

Sounds like your truck was in active regen. It needs to do that periodically to clean the diesel particulate filter (DPF). It uses fuel to burn the soot out of the filter. The process takes about 10 to 15 minutes or 10 to 15 miles. Mileage drops significantly while this is happening.

 

You probably were in a regen process when mpg were low. When done it will climb back up.there are at least 100 threads on fuel economy and regen. Search and enjoy ready.

Also welcome to FTE.

 

Thanks for the input, as the reign happens so fast I could have missed it for sure, it just seems like it happens a lot, this is my everyday driver and I will travel 150 miles a day on a average.
Guess I will just keep a eye on it and see, thank for the response.

 

Normal driving the truck will do a regen every 150-200 miles depending on your city/highway mix. Might just be getting your daily regen.........

 

Hi Racetrack,

My associate Crystal might be able to assist with your mileage concerns. You can PM her on our FordService profile here: https://www.ford-trucks.com/forums/p...newpm&u=574652

I'd be more than happy to help with your SYNC concerns, however. PM your VIN and I can provide troubleshooting assistance specific to your vehicle equipment.

Antonio

 

Antonio, he doesn't have enough posts to use the PM system yet.

 

Hi 720Deere,

Thanks for the heads up! The rest of our team can be reached on Twitter via @FordService or you can contact our Customer Relationship Center at 1-800-392-3673, options #1 then #5.

Antonio

 

I have a similar issue but it's kinna different. Gonna take some words to outline the problem.

Truck is a 2014 SuperD, 3.55 and 20" tires w/1700(or so) miles. I've had several instances where the mileage goes to hell in a handbasket.

First: Drove 70 miles running 65 and 75mph pulling a 3500# boat/trailer. First part of the trip was 65mph and I was averging 16-17mpg. The second leg(no stop just a speed limit change) was @ 75mph and the mpg avg. stabilized at 14.5mpg. I stop at a friends house for the night. Break the boat loose and go fill up in preperation for 300 mile trip the next morning. On the way back from the gas station(a 5 mile run @ 55mph) I'm averging 17-18 mpg.

Next morning the convoy heads out. Going through a residential area @ 35 mph. I'm seeing 8.9mph. Don't think much of it at the time. Hit the highway w/55mph speed limit. Truck struggles to hit 12.0mpg. Mostly 11.8-9. Eventually it hits 12.0mph. Strange I think.

Hit the major highway where the speed limit is 75. Bump it up to 75 and there is no improvement in mileage. All in all drove 750 miles, most of it hwy miles(65-75 mph) and avg'd 12 mpg. Horrible I thought.

On the return trip MPG avg. was still in the 12 mpg range. Soooo... Decided I'd slow to 55mph. After 5 mins. @ 55 mph the avg. remained at 12mph. I do understand how avg. works but what I'm refering to in the instant readout. It never got above the blue bar the MPG average display generates. Sooo, I stop, turn the engine off diddle around with the trailer then crank the engine. Back on the hwy. I start off at 55 mph. getting an average 17-18mpg, bump it up to 65 mph. MPG avg. drops to 16-17 mpg. Bump it up to 75 mph. Avg MPG goes to 14-15mpg.

Pull off the hwy. again. Turn the engine off wait a few minutes then crank it up again. Pull out on the hwy. go straight to 75 mph. Mpg avg. drops to 11.8-9 and slowly builds to 12.0 and stays there. Stop again, shut down engine wait a few minutes the crank it and do the 55-65-75 routine again. MPG is 14-15 - again.

With 1500 miles on the truck I check the DEF screen. It says "Less the 1/2 tank remaining". I purchase a 2.5gal DEF jug from Ford. Start pouring the fluid in the DEF tank and at around 1.75-2.0 gals. the tank over flows.

The dealer says I need to get at least 5000 miles on the engine and my milage will improve. I don't doubt that. But I wasn't complaing about poor mileage. It's the extremely erratic mileage and the ability to impact the mileage by slowly building up speed. I feel that something isn't right.

Yesterday. Drove to the dealer, 12.5 miles. I had reset Trip 'A'. For the most part it's 65 mph. Running empty I avg'd 12.5mpg. On the way back I reset Trip 'A'. Get back home after driving identical route and the avg. is 19.2mpg. Anybody gotta clue?

 

I have had that happen as well, kinda crazy.
I am going back to the dealer , hopefully thay can help, if not I will be looking at options to increase the mileage

 

There is a reason that the owners manual says specifically to not pay attention to the fuel mileage until the break in of the engine is done. I would say a new engine being broken in is the reason for the erratic up and down. Also you should purchase a Ford DEF Nozzle so your tank doesn't overflow. In the winter time if you overflow it, it can freeze and damage the tank.

 

Another thing to keep in mind is that a diesel has no spark plugs and will get consideraly lower mileage until the engine is totally heat saturated. Usually 15 to 20 miles at hiway speeds.

 

Ok, so just to clear this up as I did not do it before. I am a long time owner of Diesel pick trucks, 6.9, 7.3 , Duramax and now the 6.7.
The Duramax was a laps in making a good decision. LOL
My truck has 30k so I think it broke in, I am trying to work tis out with my dealer and will keep you posted, if I can get rid of the sync issue then I will be one ahead.
Thanks for all the input, good stuff!

 

I would be hand calculating your milage before I got to worried about the truck actually getting bad milage.. Just because the screen says you're getting 12 doesn't necessarily mean that's what it is.. Yes a bit annoying that it doesn't work properly but I'd rule out that first.