Grille Guard and Milage -- And other diminishing factors

[Lost_Penguin_Expy]

Happiest of Monday morning to you all. Lets jump into it...
2016 Limited EL 2wd. Averaging 13-16 half city/hwy. We had been getting 18+ for a couple of years, 19+ on long hauls on hwy.
I put a Frontier Grille Guard on our Expy shortly after purchasing (MPG number above are reflective of having the bumper on). Wife recently extended her daily commute to work and I have been wildly disappointed in the milage she's been getting. I am curious if anyone has put together any before after numbers of adding grille guard and full replacement bumpers and their diminishment of MPG. I am certain it causes a decrease by disrupting the areo and slip stream stuffs. But I can't imagine the weight of a grille guard (not heavy full replacement) would make a huge difference.
I replaced the spark plugs back in August or so, gapped to recommended spec, using FORD OEM, The ones I removed her in real rough shape. I thought it would make a huge difference, but no.
While doing plug job, i pulled the throttle body and cleaned it up as well. It wasn't too dirty seeing as it had been replaced a year before on the TB issues. Pulled MAP/MAF and cleaned all three. The MAP on top of Manifold wasn't soaping wet/oily but was clearly stained brown.
Changed air filter as well at the time.
I am currently at a loss for the diminishing MPG. I expect low teens running around town, but Highway I should be getting 18 or better.

What do you all think? Wallnut the valves? Clean intake? Any other issues I'm not thinking about? Not getting any codes. No misfires. Smooth idle. No check engine light. Only issue weve had since ownership was limp mode activated by the Throttle body issues, but that was quickly resolved.

TIA
JWB - WF,TX

 

[JamaicaJoe]

I have a 2013 5.4L 3V and made a 500 mile round trip on highway. On the way back I got 15.3 and was sort of disappointment until I realized that nearly 45 minutes was spent idling for a couple miles and that cruise control was impossible on most of the trip. I was also driving quite spirited when I could.

 

[chuck s]

Slow down. Speed kills fuel economy. And we all know that.

A large factor in fuel use is to air resistance. Air resistance is exponential and related to the square of the velocity (speed). The square of 50 (mph) is 2500. The square of 70 is 4900 or two times (2x) the resistance it was at 50.

Personal example: Towing my small travel trailer Cleveland to Gettysburg, an even 300 miles, at 70mph required a fuel stop. Towing at a bit over 50mph didn't. And the time was the same at either speed due to the requirement to stop and get fuel when driving faster. Seems "I can drive 55!"

-- Chuck

 

[BigRed2004]

@Lost_Penguin_Expy, have the tires been checked for proper pressure? Not necessarily the factory specs but the tires specs? If they are becoming deflated you’ll get more rolling resistance. Which can lead to a drop in MPGs.

 

[00000]

All common sense approaches - might be helpful to post

more info (perhaps with existing site framework everyone

could have a brief snapshot of an expy's present status)

I've run into this one = lightly sticking brake pad(s) =>

nowadays easily diagnosed w/ a thermal camera . . .

 

[Lost_Penguin_Expy]

@Lost_Penguin_Expy, have the tires been checked for proper pressure? Not necessarily the factory specs but the tires specs? If they are becoming deflated you’ll get more rolling resistance. Which can lead to a drop in MPGs.

Tires are in good shape, I check PSI often per tire's specs. Not under inflated, that is certain. I drive very sensible whenever I am driving her Expy. I have long been obsessed over watching MPG and LIE-O's, as well as calculating at fill ups. I am leaning toward a filthy intake. The MAP sensor on top of intake was pretty nasty. I am going to check again this weekend and clean again if necessary. Either that or something else engine related that isn't registering to throw a CEL.
IDK! Myabe its just the more expensive gas gets, the worse quality it becomes? HA!

 

[BigRed2004]

When you were getting 18+ on the highway do you know if environmental factors or physics were helping? Environmental for instance could have been a tail wind. Or physics could have been a draft effect off a vehicle in front of you. Getting 16 is closer to factory spec, and as long as you aren’t below factory spec I wouldn’t stress too much. There could have been circumstances that you don’t remember that contributed to those temporary gains.

 

[Lost_Penguin_Expy]

When you were getting 18+ on the highway do you know if environmental factors or physics were helping? Environmental for instance could have been a tail wind. Or physics could have been a draft effect off a vehicle in front of you. Getting 16 is closer to factory spec, and as long as you aren’t below factory spec I wouldn’t stress too much. There could have been circumstances that you don’t remember that contributed to those temporary gains.

No. We were getting the better fuel milage for a period of time, not a couple of special trips that got better milage. Were in north Texas, so were driving primarily flats, a few rolling hills on occasion but nothing extreme.
I figured changing plugs a while back would have helped, the old were filthy with the runner marks on the porcelain of all the plugs. Perhaps, the engine is simply tired at 102k miles and it should come to be expected.

 

[BigRed2004]

No. We were getting the better fuel milage for a period of time, not a couple of special trips that got better milage. Were in north Texas, so were driving primarily flats, a few rolling hills on occasion but nothing extreme.
I figured changing plugs a while back would have helped, the old were filthy with the runner marks on the porcelain of all the plugs. Perhaps, the engine is simply tired at 102k miles and it should come to be expected.

Well I’m not sure what had temporarily contributed to such great gains. While it was a nice experience, I wouldn’t be concerned with anything as long as you are still within factory specs. Engine being tired at 102k, not likely, but that can’t be stated with 100% accuracy either. Best of luck to you on your journey, and hopefully your truck continues to serve you well.