29MPG Highway :( - Unofficial Honda FIT Forums

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29MPG Highway :(

  #1  
Old 01-11-2019, 04:16 PM
evanphi's Avatar
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Unhappy 29MPG Highway :(

Hi All.

I just started a new job so I bought a 2014 5MT (Canada). Of course it is now winter and our pumps are on different gas chemistry which decreases MPG overall (noticed previously in my motorcycle). My r/t to work and back is 200KM, and I do this two days a week, other three days a week is much shorter commute. It is all highway, and generally set cruise control to 112KPH, or 70MPH (speed limit is 110KMH... I'm such a badass). I am consistently getting 29MPG. I've yet to break 30. This means for each trip to work I am using about half a tank of gas.

Things I've done to try to improve mileage:
Cruise control set as soon as I get on the highway, which is only about a KM from my house and work.
Tires inflated to 36PSI
No AC (winter, brrr)
No warm up, just get in and go
Just me (180lbs) in the car with my work bag. No junk in the back other than a snow brush.
NO CODES SHOWN. NO CEL.

Things that I plan to do:
Replace intake filter
Idle Learn Procedure
Clean MAF with MAF cleaner

Things out of my control that might be what are making it worse:
Winter grade gasoline
Winter tires

I'm interested to see how things change come summer...
 

Last edited by evanphi; 01-11-2019 at 04:18 PM.
  #2  
Old 01-11-2019, 04:41 PM
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when was the last time, front end alignment (toe) was checked?
 
  #3  
Old 01-11-2019, 10:15 PM
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Is that 29 mpg calculated with the car computer? Have you checked the mpg via the car while on the highway with the trip odometer reset so that it resets the calculator?

Short commutes and city driving really kill the mpg. You could average 35 highway get 25 around town and end up averaging 30.
 
  #4  
Old 01-13-2019, 04:57 PM
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Cleaning throttle body might improve things also but seem to be a bit of work on the FIT.

In some cars running the front defroster engages the a/c compressor to reduce condensation. You could pull in outside dry air to help there.

I suppose fresh transmission oil couldn't hurt.
 
  #5  
Old 01-14-2019, 07:55 AM
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Our Fits don't fare well in the cold. I can only imagine cold in Canadian standards.

How are your plugs looking?
 
  #6  
Old 01-14-2019, 07:58 AM
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I'm running 205/50-16 tires on 16x7 wheels, significantly reduced highway miles (better MPGs) to work, increase local miles (worse MPGs), inching my way to a solid lifetime average of 30 MPG at 73,000+ miles. Also note, that "on average" the dash MPG meter and the hand calculated MPG do closely track one another but individual tank fill ups can produce deltas of 1-4 MPG. Disregard the IRS calcs, which can change annually. I was just looking at reimbursements on trips but interesting to note what IRS considers the cost to drive, insurance, maintenance, etc per mile and life-time of ownership. ***Please note that the "as of date" should be 2019.01.02 ****
 
  #7  
Old 01-14-2019, 07:59 AM
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Correct "as of" date / 2019
 
  #8  
Old 01-14-2019, 10:17 AM
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Low rolling resistant tires will help. Not sure how much. I noticed an improvement when I changed tires to Michelin Energy (maybe 1-2mpg) over the factory all-season Pirellis. I think snow tires at all 4 corners is the culprit. That and 70/115 MPH/KPH.

On long trips I can get 35MPG on summer LRR tires driving 70MPH with light wind with the A/C on. My daily drive on Atlanta freeways averaging about 60MPH and some city driving is about 31MPG (no A/C) and 29MPG summer (with A/C). I've had tanks of summer driving with A/C, mostly city, that got as low as 26MPG.

If someone put heavier oil than 0W20 synthetic in, that could be a source of lower MPG. Maybe 1 MPG.

Don't expect a new air filter or cleaning the MAF to help. Modern electronic fuel injection prevents an inefficient fuel/air mix from occurring. I wouldn't touch the MAF.

A clean air-filter if the old one is seriously dirty may improve power slightly as it allows a small amount of additional air at WOT. A dirty air filter doesn't worsen MPG as the fuel injection correctly meters fuel according to the amount of air flowing past the MAF. Any throttle less than wide-open restricts airflow a lot more than the filter. As the MAF ages, the feedback provided by O2 sensors adjusts the mixture so it stays correct.

The other problem is people inflate the performance of these cars by hypermiling or just wishful thinking.
 
  #9  
Old 01-14-2019, 11:21 AM
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Blocky winter tires and winter gas will hurt mileage so you can't do much about that. As Steve244 notes, your mileage does not seem terrible.

Every several years, we like to clean the intake systems of our cars. After they typically idle quieter and smoother. Gas mileage & drivability usually improve, but we do a lot of other maintenance at the same time so can't attribute improvement to this.

My brother just purchased a Fit so don't know if these typical maintenance items are relevant for Hondas.

Our generic intake/exhaust maintenance:

- replace air filter. Make sure air box and intake hoses are perfectly closed and sealed
- clean MAF (only with special MAF cleaner, don't touch MAF internals)
- clean throttle body. these can get really dirty fast (study forum tips regarding lubrication. Some people recommended removing FIT TB for cleaning)
- look for vacuum leaks (very important, you can listen and do a smoke test)
- Clean EGR valve - passages
- Remove and check PCV valve/gasket

A few other thoughts:

- Check spark plugs for color, gunk, wear, etc. for overall state of engine.

- You might also want to run a few tanks of premium fuel from a major firm, not local unbranded fuel. That will run some of the expensive cleaners through fuel system.

- If you car has higher mileage, your valves may need adjusting. Is the Fit 30k 60k 100k mile recommended?

- Sometimes running a fully warmed up engine GENTLY at say 5k RPM for a few miles will help clean intake valves. Not sure that is the case with the Fit.

- Gas mileage can drop if your thermostat is not properly maintaining coolant temperature. There are a few tell tales of failing thermostat (e.g. interior heat is only luke warm on the highway now).

- You might look to buy an OBD port reader or app that reads all kinds of data real time to help identify issues (MAP, MAP, water temp, ST/LT fuel trim, o2 sensors, cat temps, knock retard, etc). We have an old ScanGauge2 that some hyper-milers use but there are many other options today.

- If your electric system is heavily corroded the very small battery will not get sufficient spark to the engine, so combustion may be suboptimal. As you are in Canada maybe salt has corroded battery connections, grounds, main power terminals. You can visually inspect and try voltage drop test (bottom of this post can help explain what voltage test is- quick and easy to do just use caution for health & safety). This can also improve starting in cold conditions.

https://www.fitfreak.net/forums/2nd-...fit-sport.html
 

Last edited by Fiting; 01-14-2019 at 12:53 PM.
  #10  
Old 01-14-2019, 12:09 PM
Join Date: Nov 2010
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If I remember right 5th gear in a manual on the Fit runs at higher RPM than 5th gear on the AT. So 70 mph will get lower mileage. Especially with snow tires. How is your mileage at 60 mph? (you could reset the computer for that run, or just look at the bar graph on the dash)

Do you rev the car a lot getting to the highway?

Is the route hilly? (you use more gas going up hill than you save coming back down the same hill)
 
  #11  
Old 01-14-2019, 12:30 PM
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Originally Posted by GolNat View Post
Is that 29 mpg calculated with the car computer? Have you checked the mpg via the car while on the highway with the trip odometer reset so that it resets the calculator?

Short commutes and city driving really kill the mpg. You could average 35 highway get 25 around town and end up averaging 30.
No this is trip meter and fillup amount. This car is pretty much only used on the highway.


Originally Posted by Fiting View Post
Cleaning throttle body might improve things also but seem to be a bit of work on the FIT.

In some cars running the front defroster engages the a/c compressor to reduce condensation. You could pull in outside dry air to help there.

I suppose fresh transmission oil couldn't hurt.
Defroster is only run with pulling outside air.



Originally Posted by julianachos View Post
Our Fits don't fare well in the cold. I can only imagine cold in Canadian standards.

How are your plugs looking?
-10C or colder the past few weeks. Unless it snows.


Originally Posted by Brain Champagne View Post
If I remember right 5th gear in a manual on the Fit runs at higher RPM than 5th gear on the AT. So 70 mph will get lower mileage. Especially with snow tires. How is your mileage at 60 mph? (you could reset the computer for that run, or just look at the bar graph on the dash)

Do you rev the car a lot getting to the highway?

Is the route hilly? (you use more gas going up hill than you save coming back down the same hill)
60MPH is a little too slow for comfort on our highways around here. I imagine it would be better mileage, though, as it sits at or just below 3K RPM at that speed in 5th. I drive this car like a granny whenever possible. Trying to save money, seeing as how we had to buy this vehicle for my new job.

And the route is not excessively hilly.


__________________________________

Consensus seems to be winter tires and fuel suck. With the weather we have and the amount of driving I do, all four winter tires are staying on! I'll report back in the summer once better tires and gas are back! I'm also going to compare it to our HRV.
 
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