Honda Tech fairy wand is worth a +rep to you draw2much. It's been known to work! Low tech calculation at each fill-up will tell the truth, as well as vouch for the MM [in]accuracy. I will question the 3-4mpg going out the window with AC, however, it does have an effect. The Texas heat/humidity - well possibly. It's a rather efficient system. Coyote can possibly provide a dusty report. 3mpg at most, but it is worth it, no?

 

@Krimson_Cardnal,

I repair and improve computers as a hobby. I've been on the other side. Sometimes a machine just needs "the tech touch". xD

I'd probably die of a heat stroke if I tried to drive in a car without an AC right now! We don't have a lot of humidity in North Texas, but the sun is scorching regardless. If it's just a matter of it being stupidly hot and the AC running all the time, I can accept a financial blow at the gas tank.

 

I managed an engineering design office's computer system for a while - my key tag line was always, "Computer's do funny things." That's what I thought when you brought out the fairy wand. With the Fit's overall economy it's hard to think penny pinching the AC.

Keep an update on the MPG's - interested in seeing how it works out. Hard for me to link it to the recall work...

 

What year is your fit? The 2009's had the fuel economy calculator off by about 4-5mpg but with the update, mine's only really ever been off by 1-2mpg so it's pretty close (and it's always 1mpg HIGH) so it is predictable. the '10 & '11 are the same from what I've read on here so it's pretty accurate. (it won't be off by 3-5mpg).
I'd recommend using the ODOmeter instead of the Trip to calculate the economy. over the life of your vehicle, those tenth's add up. That's what I like about the phone apps (plus I don't have to keep a notepad in the car like in the "olden days").

It's scary but I've been doing this too for close to 20 years. Old Cyrix Overdrive processors that literally snapped over top of the 386SX 20mhz. Still do it on the side except I've bumped up a little bit working for some local Doctors. Providing remote Access via VPN to their offices, etc... But I still do the ever present memory upgrade and spyware cleaning.

As for the A/C I think you'd take a 2-3mpg hit if you run it all the time. I end up at times with a 4mpg hit but that's because I'm often upwards of 40mpg and the higher your economy goes, the more of a hit you'll take when you turn the A/C on. Here in VT, I'll use it once a week most of the time in the summer and i'm usually around 41mpg. On a nice warmer week (but not too hot) where I don't need to use A/C at all, I've been at 42. When I have to use it all the time, I'm at 38.

What speed do you usually run at on the highway. My economy numbers are due to the fact my average speed hovers around 45 with only a few stop signs and 25mph towns. I find that when I maintain over 65, my numbers drop. At just under 80mph, with the family in the car and a cargo box on the roof, I averaged 29mpg on Strictly highway. If I had the A/C on, I'd have been at 27 or 26 probably.

My wife refers to me occasionally as "Nick Burns, your company's computer guy" - If you aren't sure what it is, look it up on youtube - it's an SNL thing. I currently am into "laying of the hands on..." on computers. I walk up to them when people have problems, place both hands on them, bow my head quickly and squint like I am sending my energy into the computer. then pop up and look at the ceiling, return to a standing position, and say... it's fixed. My staff looks at me weird but it works. They click too damn fast and don't let the computer catch up... the theatrics gives the computer a breather and all is right with the world. The best is... they ask What I did to the computer to make it work... like they weren't there to see the whole thing.

~SB

 

Guru magic!

 

I just want to pop in and give an update.

Nothing is solved.

I ended up having to buy new tires, and the standard size for the Fit was too expensive (or would take too long to get to me). I went with a larger size, 205/50. Getting the larger tires means my MPG drops even more. *sighs*

I'm not even bothering to take it back to the Dealership. There's no way they'd believe me and there'd be no way to prove it since the larger tires would automatically skew the results.

I haven't gotten over 29MPG in quite some time. I got 31 MPG maybe two or three times during a 4 day drive from TX to FL, but most of the time it never got more than 30 MPG. And that trip was last year.

Oh well. I'll just live with it.

 

just my 2 cents... if the MPG issue annoys you enough (and it would annoy me), i'd go back to the dealer, or a different dealer, and get their best mechanic to do a valve adjustment on the car.
it seems very reasonably to presume the valve adjustment during the recall is what reduced your MPG.

 

My daughter had recall done on her 09 Sport about 4 months ago. Last month she got a check engine light (cel). Dealer pulled codes P0302 / P0303 miss fires in cylinders 2+3. They replaced the coil packs on 2+3. Last week CEL came on again and same codes. They reset the light and drove with scan tool connected and had 8 miss fires on cyl 2 and 13 on cyl 3 . They let it sit over night and checked valve adjustment in the morning and #2+3 were out. Retested after adjustment and no miss fires. I asked her afterward about her mileage and she said it went from 35 to 30. She thought it was because it was winter. I will update if light comes back. Dealer is sure this is fixed. ( didn't mention that they miss adjusted at the recall )

 

Wish we knew the mileage when your coils failed. We here have formed the opinion that spark plug failures will hasten coil pack failures. So far in only a few cases we have replaced plugs at 40k and not one has had a coil pack failure in 60k miles, not our usual expectation. plugs are a LOT cheaper than coil packs. Misfires are equally the result of bad plugs as coils so if plugs weren't replaced the bad plug)s) could esily reset the light.
Any time coil paks are replaced the plugs should also be replaced. Regardless of the schedule or warranty, plugs just don't go much further than 50k without self-destructing. Its the harshest conditions in any internal combustion engine and its a miracle hey last that long.
Valve adjustment can affect mpg but unless seriously out of adjustment not likely to cause plug or coil failures.
And yes short trips in cold weather will deteriorate mpg.
Good luck.

 

They replaced the coil packs first then the valve adjustment. Personally I don't think the coils were the problem. I think the valves were. The CEL came after the motion spring recall. My understanding is that it takes a certain number of miss fires to trigger the CEL (check engine light)

 

Draw2much,

Did you happen to change over to synthetic oil by chance at about your mileage drop? Years back in my tricked out VW Scirocco days ( detuned Super V stroker motor with dual side draft Webers, nitrous oxide, gutted, and 12 point roll cage.) I could tell seat of the pants HP changes very easily, and was known to be accurate when some car friends did changes and paid for dyno time.

Back in the late 80's early 90's if I would fill my motor with full synthetic I would feel a HP drop. I even got as far as talking to a Mobil oil engineer about this and of course that was the time they were touting increased mileage with synthetic so he discounted my findings.

I never paid for dyno time, but if I drained the synthetic of any brand or viscosity and put in even 20w 50 I would get a seat of the pants HP increase. Just enough to tell. A couple other guy could feel it too. They of course like me then did not use synthetics after that for our High perf street cars. No idea if it is that way now. I use synthetics on my Fit now for Minnesota winters every year. But use dino oil in summer.

I know it sounds obscured and goes against all conventional wisdom, but all you had to do is fill and drive and for most they would say WOW , your right, less HP. Not saying this would even correlate into even 1MPG of your problem, but I had this in my head from years ago and thought I might as well write about it here.


My 2009 Fit gets 28-30 in town with small hwy stints to work.( after mileage meter was re-flashed) Highest on hwy trip 36 ( on paper old way) I had the recall on valve train done and I saw a little seat of the pants reduction of HP and did not really see a mileage change. In my younger year I would be pushing Honda about the HP reduction but at 50 years old, with kids, who cares.

 

Nonsense.
Private shops and Mobil oil tests on dynos and in the field both show increases in HP and mpg when oil is switched from hydrocarbon based to synthetic based lubricants. Sure, you can get less mpg and power by switching friom 0W-20 standard to 5W-50 synthetic or by not changing thed filtger but thats not accurate test. As for set-of-the pants detecting hp changes on a Fit ...
Try suing Mobil for false advertising and see how quickly they blow you - and your assets - away.

 

Or maybe, because you were running a hot nitrous motor with fat piston to wall clearances the thicker dino oil took care of some of your blow-by and increased dynamic compression..

Which has jack-all to do with a tight clearance stock Fit, where a 0w syn would have less parasitic drag.

I actually have the numbers on here somewhere demonstrating the power lost to friction on a 10w30 dino oil per main bearing.

 

draw2much,
I have had the exact same problem with my 2009 honda fit. I was getting 38-39 mpg, and it has dropped to 33 mpg, after I left the dealership/recall. I was hoping that you had made progress in finding a resolution.