Took the car for a long run - Wash DC to NYC and back,
first tank got me 250 miles, second tank 280.
was driving with the AC off, clear roads on the way there and back (2am drives)
Tires are 35psi on all conrners

No fault codes on the car's registry.

any ideas what can i check that would lead to such bad MPG?

 

I'm curious to know what MPG you had been experiencing before the trips, during the trips, and after the trips. I never gauge anything by the miles per "tank-full" if that is what you're trying to do. Way too many variables on when you decide / how you fill up. What are the actual MPG numbers for the hand-calculation based off of the gallons purchased each time?

My '11 Sport AT has averaged 30.5 MPG over 377 fill-ups of all different volumes with "regular" gas from many different vendors in "hilly" Pennsylvania but we don't have anything close to the traffic situation that exists in the Baltimore / WDC Metro-area, so your results may vary.

 

Have you hand calculated your MPG?
IMO the warning light, is pretty conservative. You say your MPG is poor, but are only offering how many miles you've driven between fill ups. Without knowing what your actual MPG is? Impossible to answer.

You need to take note of the amount of gasoline being put in your tank at fill up, and then use that number divided into how many miles you've driven on that tank.

If I fill up aggressively with The Fit? I can be putting in less than 9 gallons of gas at fill up.
So in other words, if I put in 8.5 gallons, on a 240 mile tank, that works out to 28+ mpg. 280 miles driven would be 32+ MPG, which is the reported EPA average for my 2016 Honda Fit.

So really the first step, is to figure out exactly what your MPG is...and not by the computer. By hand calculation. Distance driven between fill ups...is only distance driven between fill ups. The Fit has a pretty small gas tank....which means cheaper fill ups...but more frequent, regardless of MPG.

 

i can be clearer -
car is getting below 23MPG no matter what (since i bought it, about 6 months ago)
car has 140K miles on it

these specific trips were just a good opportunity for me to get accurate mileage read -
first fuel was 9.8 gallons, second was 10.1 gallons, with the respected mileage info above - this does not even come close to what i was expecting for driving constant ~70 MPH during the trip.

i guess my question is what factors (beside tires, air filter and alignment) can impact the fuel consumption?

 

Several yrs ago, my MPG dropped over a month down to 22 mpg with no change in driving habits. At the same time, I was getting an odor of gasoline upon start up. Eventually, the Check-Engine-Light (CEL) came on indicating "misfires". Obscuring the obvious was my '11 was first yr for Vehicle Stability Assist (VSA) and that light came on at same time as CEL and I was wondering about the ABS system.

Turned out that two spark plugs had worked themselves loose. I bought the car new off the lot and no one ever serviced the engine (approx 25K miles) except for oil / filter / engine air filter / tires. So, loose plugs was last thing I would have thought would happen.

This might be something you could check on your own or have a mechanic do it. If on you own and you don't want to off the windshield wipers, plastic cowling, and metal bottom tray of the heating / air conditioning system to get at the back of the engine, you can do it with your left hand and a vivid imagination. Many of us have done it. Pinch the wiring harness at each coil pack to disconnect and then 10mm socket removes anchoring bolt per pack. I cheated and looked at the wife's '09 CIVIC where all of the plugs, wires, coils are on the front of the engine and I could see how to pinch the wiring harness to get a release.

Once you have the coil packs off, look / smell each one. If brown / black soot and odor of gasoline, that plug is the problem.

 

spike, can you really remove spark plugs with the under-windshield tray in place?? that's great!

OP, 23mpg for highway driving is well outside what you should expect @70mph with OK tire pressure. I agree this indicates a problem somewhere.

Plugs are a good place to start. If you don't know if the plugs have been replaced, keep in mind the interval is 100K, so that may translate to "never" int the mind of the original owner. If that doesn't work. If your coil packs were bad I would assume that would throw a code, same thing with O2 sensors. You could try cleaning the MAF sensor gently

No other symptoms? Down on power, smoke of any color from exhaust, noises, vibration, oil residue around engine? Engine and transmission oil are recent and trans shifts OK? If no other symptoms it's really hard to know where to start beyond plugs. The one crazy idea I have is the parking brake adjustment .. nothing electronic there to throw a code but it could be slightly engaged. Same thing with rear drums. I feel like those are less likely than old plugs though.

 

It can be done without removing the tray but you won't be able (at least I wasn't) to fit a torque wrench in that space. I did it left-handed in the dark the first time but then another plug came loose (ultimately #2 & #3 were the problems). So I decided to start with new plugs, torque everything to spec and removed the tray. A few thousand miles later one of them were loose again. That's when I did it left-handed in the dark (sort of like unhooking a bra snap left-handed in the dark - a now little used skill from 40 yrs ago ) and used some blue threadlocker on each plug without a torque wrench. Good for the last approx 30K+ miles.

 

Thanks for the detailed reply.
Is there a "preferred spark plug brand" for the Honda engines?
My S2K likes NGK, anything special that the Fit would like?

Also ordered valve cover gasket, will be adjusting my valves this Friday, might as well change the spark plugs while im there.
I've also read about the coils, i will be testing them when they're off the car using a multi-meter.

Regarding "other symptoms" with the car - i don't have any reference to how the car should behave, but it does feel a little "slow" or "weak".
gear change is fine (despite a tendency to down-shift too much for my liking)
car is mostly empty (my wife's yoga mat is the heaviest thing inside)

Will update on Friday / Saturday after i've adjust the valves, change the spark plugs and go for a spin

 

check the alignment, you can use simple fishing line and jack stands or alignment toe plates (my fav)

as the others said, spark plugs and maf cleaner

perhaps pop in a new engine air filter, those are cheap enough

shed as much weight from the car as possible, yoga mats gotta go!

try to inflate a few extra psi into those tires

maybe dump a bottle of techron (or your fav inj cleaner) to be thorough?

 

I'll do my standard line: don't automatically change out good coil packs. Yes, test them and if bad swap out. Even at $75 / ea, it's $300 better left in your pocket. I can't remember seeing (I have very bad eyesight ) one person on the forum saying that they had a bad coil pack but several have changed them for the heck of it. Interesting how people "problem-solve".

 

OP, just 1 more thing. perhaps try your luck the Fuel Mileage sticky thread?

https://www.fitfreak.net/forums/3rd-...scussions.html

 

OK..but you do realize that information conflicts?

I'll take the liberty of simply rounding up and down respectively to 10 gallons each fill up, to keep it simple.

" First tank got me 250 miles, second tank 280. "

Divided that by the 10 gallons (roughly) you were putting in the vehicle and you end up with an MPG of 25 mpg, and 28 mpg respectively. Which is more than 23 mpg.

But it's your vehicle, and if you say it's only getting 23 mpg gallon or less? I'll just give you the benefit of the doubt. And I'd say if you are only getting 23 mpg, then my ignorant response would be....something is significantly wrong. Look at all the advice being given, and maybe check everything out. You should be getting better gas mileage.

Best of Luck, and let us know if you discover the problem and fix it.

 

Fitchet,
i get the facts check and everything, but i think you're missing the point -
the cart is known for making +35MPG on highway drives, even if i was getting 28MPG, this is still 20% higher than mileage it should be doing.

could it be the match doesnt add up? yes, maybe, but it does not blur the main issue - fuel consumption is not ideal on my Honda Fit.

As for handling the issue:
Air filter changed already
got new spark plugs
got new valve cover gasket
got a filler-gauge
got 6 cans of fuel-and-engine cleaners (Techron)

and in 15 minutes of so i am planning on diving into valve adjustment procedure.


Will update once done

 

Not saying you don't have a problem that needs to be fixed.
I'd be highly disappointed if I was doing a long highway drive, and only mustered 28 mpg. I'd expect more.

As I said, if you're only getting 23 mpg...something is wrong.

I'm actually staying tuned...to see if you can bump that MPG up.

 

I would replace the plugs. Our daughter's Fit was getting 16-18 mpg in city driving, but when I replaced the plugs the MPG jumped up to 24-26 MPG in city driving. Also all 4 plugs were very loose.

 

So the plugs being loose was the cause of the poor gas mileage not that the plug itself was worn out after 100,000 miles. Back in the old days it was: points, plugs, and condenser twice a year but not the case anymore.

 

 

So on Sunday morning i finally got to perform the tedious job of adjusting valves and replacing the spark plugs on my Fit.
it was not a quick task, nor was the access to the engine as easy as in my S2000, but still, it had to be done, and 4 hours later, it was done with success.

Just for context, the car has 140K miles on it.
i have the full carfax report of it, up until i bought it it was handled in a Honda dealership and than @ a MIDAS auto shop near where i live.
it is not mentioned in the carfax or maintenance report that the SP were ever changed, and it certainly looked and felt like that when i took them off.
as for the valve adjustment, again, i have no reason to believe this was ever done to the car.

So the findings:
1. As far as valve adjustment, i used this video:
its only 5 minutes long, but it covers the job very well.

2. I was surprised to see that only limited amount of valves actually needed adjustment, and the variance to spec was very very low.
on all of them the adjustment required was to loosen them (they were too tight) and not the other way around.
for some reason, i was expecting it to be the other way.

3. For the spark plugs, like mentioned here before, they were very loosely tightened to the engine's head.

4. the spark plugs were also very worn, you could can see in the pictures the new SP gaps vs. the worn off gaps of the older spark plugs.
if with older engines, the electrode would corrode before the metal was eaten, now its the other way around, and the electrode is actually getting consumed before corrosion and residue build-up is effecting the SP performance.

and the results of the job?
The car feels much more responsive and like it has more power.
as for the fuel consumption, i still didnt get a read out yet, but i believe it will improve. only question is by how much.

i will update once i get some mileage on the car.

BR


Which valves required adjustment

Close up for comparison - 140K miles vs 0 miles SP

140K miles old spark plugs

comparison - 140K miles vs 0 miles SP