17mpg at 68mph?!
Thanks everyone for the feedback and I enjoy the dialogue. Maybe it does have something to do with the winter blend. I'm not a speed demon when it comes to driving, as I usually keep it between 70-74 on the interstate. I know I didn't get a truck for MPG, however I came back to Ford because I had almost the same exact truck before that would get 20mpg easily at 70mph and it was comfortable for long trips. I absolutely LOVE my Ford truck, but 4mpg makes a big difference when driving 3,000 miles/month.
I've taken the truck out this morning and set it at 70mph and was only seeing low to mid 16's. I sure wasn't expecting a 4mg decrease!!
My truck has stock tires, truxedo low pro bed cover and K&N CAI. The only difference is the gearing....would going from 3.15 to 3.55 cause that much of a significant difference?
I've taken the truck out this morning and set it at 70mph and was only seeing low to mid 16's. I sure wasn't expecting a 4mg decrease!!
My truck has stock tires, truxedo low pro bed cover and K&N CAI. The only difference is the gearing....would going from 3.15 to 3.55 cause that much of a significant difference?
Senior Member
Joined: Apr 2013
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From: Winfield, IN
The gearing will make a slight difference, maybe 5% or so, but definitely not 20%. I see you have a K&N air filter- those filters are oiled, so there is a slight chance your mass airflow sensor could be gunked up with that oil. One thing to try would be to get some MAF sensor cleaner from your parts store and clean it off.
Senior Member
Joined: Apr 2013
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From: Winfield, IN
If you look at the signatures of the eco guys who talk about getting 20 something at 70, it is usually 2wd trucks with 3.15's or so. Beyond that, there seems to be a lot of variation in eco numbers.
My 6.2L max tow (3.73) pulls around 15.5 mpg @ 70 mph empty so I would say your numbers feel a bit low for an eco. I think your only option is to trade time for money (slow down).
My 6.2L max tow (3.73) pulls around 15.5 mpg @ 70 mph empty so I would say your numbers feel a bit low for an eco. I think your only option is to trade time for money (slow down).
Mine is a 2010 5.4L. I'm just trying to figure out why a previous F150 supercab that I had with the same 5.4L 6 speed tranny would get 4mpg better mileage. 
Does anyone have any experience going from 3.15 to 3.55 with the same engine/tranny?
Does anyone have any experience going from 3.15 to 3.55 with the same engine/tranny?
Junior Member
Joined: Sep 2013
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My new F150SC 4X4 twin screw is averaging 14.5 mpg. Cab height fiber glass topper was expected to help improve the mileage. It's only got 2800 miles in less than 3 weeks so I'm hopeful it will improve with time.
The gearing will make a slight difference, maybe 5% or so, but definitely not 20%. I see you have a K&N air filter- those filters are oiled, so there is a slight chance your mass airflow sensor could be gunked up with that oil. One thing to try would be to get some MAF sensor cleaner from your parts store and clean it off.
Senior Member
Joined: Apr 2013
Posts: 2,733
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From: Winfield, IN
A fiberglass cap will probably actually decrease fuel mileage. Any gain in aerodynamics will be offset by the added weight, around 200 lbs or so.
Senior Member
Joined: Apr 2013
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From: Winfield, IN
Great suggestion, thank you. I was wondering if the K&N could have anything to do with it. I did freshly oil it before taking it out for the first time, although I let it sit overnight before driving it. I tried not to apply too much of the aerosol oil, but I guess there's a chance I did.