Fuel milage decreasing
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Joined: Oct 2017
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Fuel milage decreasing
I have a 2016 F250 4x4 6.7 biodiesel with 39000 miles. I run mostly flat interstate at 80 to 85 mph. milage has gone done from 14.7 to 15 down to 13.9 to 14.3. any ideas to improve milage? i've changed the fuel filter. what about a performance chip? thanks for help.
Senior User
Joined: Aug 2016
Posts: 164
Likes: 1
From: Olympia, WA
It is that time of year where we are running into colder mornings, and longer warmup times which will have a minor impact on fuel mpg. Add that to tire pressure, and that could explain the difference you are seeing.
So that said, I would start with tires, make sure your cold pressure is good. All 4 of your tires may have lost 5 to 10psi depending on where you live, and that makes a dent. And if all 4 loose about the same amount of pressure, the TMPS will never be the wiser, well unless you really lose a lot.
Also, look at your warm up times, specifically your transmission. There is some magical process in the engine to help it and the trans come up to temp, and that tends to squeeze 1 to 1.5 mpg away. I know I see it with the trans. On cold days, the engine still comes up to temp pretty quick, but the trans takes a little longer. Watch it in the disply, you'll notice your "realtime" MPG goes up usually after the trans temp hits something >150f.
I will hope and say that is the difference you are seeing. To go deeper into the engine could be a bunch of stuff, but not likely at your age and mileage. Start with the easy stuff.
So that said, I would start with tires, make sure your cold pressure is good. All 4 of your tires may have lost 5 to 10psi depending on where you live, and that makes a dent. And if all 4 loose about the same amount of pressure, the TMPS will never be the wiser, well unless you really lose a lot.
Also, look at your warm up times, specifically your transmission. There is some magical process in the engine to help it and the trans come up to temp, and that tends to squeeze 1 to 1.5 mpg away. I know I see it with the trans. On cold days, the engine still comes up to temp pretty quick, but the trans takes a little longer. Watch it in the disply, you'll notice your "realtime" MPG goes up usually after the trans temp hits something >150f.
I will hope and say that is the difference you are seeing. To go deeper into the engine could be a bunch of stuff, but not likely at your age and mileage. Start with the easy stuff.
Lead Driver
Joined: Jan 2005
Posts: 7,782
Likes: 221
From: Huntington Indiana
Very true... when I get above 65 fuel mileage heads south.
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Tuned
Joined: Jul 2017
Posts: 316
Likes: 13
From: Wautoma, WI
First guess if nothing else has changed is winter blended fuel. It's always right around this time of year I begin to question why my mileage tanks. It's always the fuel
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Fleet Mechanic
Joined: May 2011
Posts: 1,866
Likes: 84
From: Rainier OR
yep, nothing you can do, and no amount of money you spend, will make as big of difference as slowing down to under 60 mph. I really comes down to physics. It might on take 100hp to move your truck at 60mph, but it COULD take 200hp to go 85mph. You need more fuel to make the extra hp.
Post Fiend
Joined: Mar 2007
Posts: 26,966
Likes: 50
From: Texas
Being at the right place in the torque curve is my guess.
Postmaster
Joined: Jan 2009
Posts: 2,667
Likes: 1
From: Glen Rose,Texas
Wow
Chris...that is fast driving for you
My 12 will not get better that 15 no matter what I do but I never use the mpg screen.I look at the temp screen all the time.
No worries,if I want fuel mileage I get in my 02 with 356k on it.
Chris...that is fast driving for youMy 12 will not get better that 15 no matter what I do but I never use the mpg screen.I look at the temp screen all the time.
No worries,if I want fuel mileage I get in my 02 with 356k on it.
Post Fiend
Joined: Mar 2007
Posts: 26,966
Likes: 50
From: Texas
Well in my defense, it really doesn't feel that fast in these new trucks. And my father in law has had some health issues lately so we've made lots of trips up towards Denton, which gets to be a bit of a drive.
Senior User
Joined: Aug 2016
Posts: 164
Likes: 1
From: Olympia, WA
I think you could just stop at the word Texas with that one. I am not saying they drive bad in TX, but damn do they drive fast 
. I am just guessing, but I think the minimum speed limit on your freeways is 5 over whatever the posted sign shows, and that's on top of most posted speeds that seem to be 70+.
So naturally fuel MPG and TX do not always sync. Still, truck does get good mpg at some of those higher speeds. Well at least empty.
. I am just guessing, but I think the minimum speed limit on your freeways is 5 over whatever the posted sign shows, and that's on top of most posted speeds that seem to be 70+.So naturally fuel MPG and TX do not always sync. Still, truck does get good mpg at some of those higher speeds. Well at least empty.