Help gas mileage terrible by the day
 

My 2015 fit now has 28000 miles on it and I been noticing my mileage has been going down slowly each day. A full tank would give me about 200-225 and my avg on my gauge shows 30mpg and now its 27mpg after 93miles driven on a full tank. I will be changing my CVT fluid and oil change this weekend but anyone else have this issue? Any tips on what I should do? I get top tier gas and dump a bottle of chevron fuel system cleaner every 9k miles when I change my oil. I did have a few times check engine light turn on and believe it was related to the fuel cap not being tight enough, forgot the code but remember it being very small fuel/ emission leak

https://cimg9.ibsrv.net/gimg/www.fit...9d75f547c2.jpg

I would top up the gas tank, make note of mileage, and do this for a few tankfulls, noting the miles since the last refill, and manually calculate mpg....the mpg gauges can be inaccurate, but if you're getting 200-225 miles on a tank, something has to be wrong, hopefully something minor. Wish I had more to offer. I typically go 320 miles before refueling, can never get more than 9 gallons in at that point, if even...

Friendly reminder, there is a sticky thread for fuel mileage related discussions = https://www.fitfreak.net/forums/3rd-...scussions.html




Back on topic:

I've got more miles than you, and higher mpg's

Could it be something simple?

-low tire pressure?
-dirty filters?
-new commute?
-new bowling ball in the back seat?
-heavier right foot?
-any changes to the car? (new "cold air" intake?)

WOW:

I have 70K miles. I beat the F _ CK out of the car with my foot mostly in the accelerator. Most of the time the car dash color is whichever the poor fuel economy color is? In addition I have 16X7" aftermarket wheels with sticky 205/50R16 tires that don't lend themselves to fuel economy and I still average 37-38 mpg.

If it's still under warranty take it to the dealer.

Stuck brake pad/caliper?
Very mis-aligned wheels?
Your tire pressure gauge is reading wrong so you're way underinflated?

A/C or Defrost left on inadvertently?

Yes start with the basics.

Also note down any check engine lights. When did they come on. How did they get cleared?

How long are your oil change internals?

Even if you are not using top tier gas, added detergent, changed the oil, drove with AC on/off, leaded foot or the tires are under.tire pressure you should be getting better mpg than what is shown. Definitely, something substantial that is causing a meltdown in mpg. First, if you are accurately measuring the mpg manually, you will notice the Honda mpg indicator is generous by 2 to 2.5 mpg on a full tank of gas. That's not the issue here. I suspect there is a gasoline leak somewhere or a crack vacuum hose. Are there a lot of black soot in the tail pipe (running rich mixture of gas/air) or does it look blue (good gas/air mixture).

the switchover to winter blend gas was made a few weeks ago and it really pushes down the mileage.in my Fit

What kind of driving are you doing? Less then 30mpg is obtainable in stop and go traffic. If your driving routes have not changed then your 3mpg drop could be the winter blend.

Fill the tank reset the trip and take it on the highway for a good 30-45 minutes and see what you get.

Thank you for all the suggestions and feedback I did look at fuel related topic and haven't pin point a solution and after 25 page I gave up.

My tires are new I replaced them a month ago and checked that they are all at 32psi. I only use the car to commute to work so I can say 85% of the miles is freeway miles and I do not drive hard. I changed my air filter to the rechargable K&N but not sure that it will affect the gas mileage. I also got brand new brake pads and rotors not too long ago but the bad mileage has been there before the rotors and pads were changed. I live in the bay area and rarely use the AC.

I do have a full system in the car which makes the car heavier and I drive with 2 baby seat all the time since after work I go straight to pick up my kids. One of the seat is 20lb the other is just a booster.
https://www.fitfreak.net/forums/3rd-...m-install.html
https://cimg2.ibsrv.net/gimg/www.fit...05aaac879b.jpg
I do suspect there is a leak somewhere and Im afraid to bring the car to the dealer because currently I dont have the funds if its something major. So Im reaching out to see if there is something I can do or change myself.

Thank you

I dont think its the gas because I see the reading at 30mpg for over a year and half now but for the past 2 months it went down to 27 so thats why im reaching out for some help. These are mostly freeway miles going about 65-70mph.


I'll go fill up now and then manually calculate the gas mileage on the next fill up.

Bump up your tire pressure. 32 PSI is needlessly low.

I run 38 PSI in my car. That'll help a bit on the freeway.

https://cimg8.ibsrv.net/gimg/www.fit...cf69178e10.jpg
I would say your exhaust look normal compared to my exhaust.

If you're in the bay area and routes have lots of hills with stop and go driving you won't get great gas mileage. That's pretty much the worse combo for gas mileage. There's really not much you're going to be able to do absent of moving.

Hey 2Rismo2 I agree with you on this one and if that was the case for me I wouldnt even reach out for help. But I do not drive downtown, I live in the outside of San Francisco the sunset and work in South San Francisco my commute is at 6am never stuck in traffic at that time and only takes 19mins to get to work about 11miles one way. I take the 380 freeway to work then home so mostly its freeway miles. I'll ask my mechanic shop to do a vacuum test and see if they can find a leak.

Are you still on the original fuel injectors? The '15's had a pretty high failure rate. I wonder if this is the first sign of injector troubles to come?

I'd be tempted to pull the spark plugs and see if any of them give signs the car is running rich.

Hi Gafit good point regarding the injectors and honda did replace them the week when the bulletin came out few years ago. And I do recall telling myself when they replaced the injectors my gas mileage gotten worst but at that time I was taking the bus to work before my office moved out of town so I never really thought about it. I do remember my gas mileage gauge was showing 39-42 before the injectors and went down to 35 afterwards. What would my spark plug looks like if its running too rich? I can take one out and take a photo over the weekend.

If running rich, plug will be black and sooty. Can be cleaned off with some carb cleaner..

I'm guessing it's all this...
 

"I did have a few times check engine light turn on and believe it was related to the fuel cap not being tight enough, forgot the code but remember it being very small fuel/ emission leak. "

And unfortunately my further guess is it's NOT as simple as simply the fuel cap not being tight enough.

From my San Jose house to nearby freeway onramp is a mile, I get 25 mpg without heavy foot, from there to offramp in Fremont 20 miles later, I get 40 mpg. That is my morning commute (almost no traffic). BUT in the afternoon commute, the same route from Fremont to San Jose, I get a range between 30 to 35 mpg due to heavy traffic.

update! over the weekend I changed my oils. It seems to be dark color, the last time it was changed was 9k ago and always with mobile 1. Before I changed my oil I check the dip stick and notice the oil was at the minimum line or at the first line. Not sure if that plays a factor in lower gas mileage but I did add 3.75qt the last oil change and same with this change. I also changed the CVT fluid since the car is at 29k miles and I went to fill up my tank and added the fuel cleaner. Its been 4 days and the car feels so much smoother from the CVT fluid and oil change. I also tried to check my spark plugs but didnt have the spark plug remover so I cant see how it looks like. The coil was dry and looks brand new and all the plugs were tight. So after driving for 4 days my gauge is reading 34mpg avg but I wont know for sure until I fill up again. But this is very promising. Could a bad CVT fluid or low oil cause bad gas mileage?

Out of everything you said here, the only thing that makes sense is the fuel cleaner that you added. Oil/tranny fluid change won't be a 7mpg difference. How long had you been getting 27? Maybe just a bad tank of gas? Or had it been a few fillips worth?

The best thing you can do is sign up for a free account on fuelly and track your mpg - then if something goes wrong you'll know right away.

Well I just left work and got a check engine light on. my obd2 adapter broke so I stop by the auto store and they pulled up the same code P0456 Evaporative emission system leak detected (very small leak) while I was at the auto store I picked up a new gas cap just since I get check gas cap many times even though I know I tighten the cap. Anyone else have P0456 code?
I think the leak might be the reason I am getting bad milege

lannym I have gotten gas at the same spot a block away from my workplace for at least 2 years mobile gas. I cant remember when my mileage went down but just 3 gas fill it went down to 27mpg. When I first bought the car I was getting 37-42 reading on the gauge.

I googled that cel + "honda fit" and this thread popped up:

https://www.fitfreak.net/forums/3rd-...ode-p0456.html

(its yours! *giggle*)

I think this is worth a read = https://www.fixdapp.com/blog/p0456

P0456 Symptoms

• Check Engine Light is on
• Decreased fuel economy <--- this one has your name all over it
• Fuel smell

P0456 Causes

• Loose or damaged gas cap
• Leaking or disconnected EVAP hose
• Faulty purge valve
• Faulty canister vent valve
• Charcoal canister leak
• Leaking fuel tank

Thanks man I now remember I ask about this code awhile ago but started taking the bus to work I didnt fully looked into it after clearing the code. I had the mechanic clear my code this morning and he said changing the gas cap would be the first and cheapest DIY thing to start with. If my check engine lights come on again then at least I know its not the gas cap. You listed the 3 symptoms and I have all of it. Sometimes after a fillup I would park my car in my garage and on 2 occasion the whole garage smelled like gasoline. I really hope its just the gas cap.

I had a similar issue with a Civic and it was some type of EVAP issue (canister or filter). Sounds like you might be on the right track though!!!

UPDATE!!

We finally found the problem. The vent valve solenoid was the issue and was stuck halfway open. Once we changed that part out my gas mileage went from 220 per tank to 380 per tank. Wish we found the issue sooner but hope this help anyone else that has similar issues.

mind sharing with us some photos of that vent valve solenoid?

https://cimg9.ibsrv.net/gimg/www.fit...4d446b949.jpeg
https://cimg8.ibsrv.net/gimg/www.fit...f36ac9c86.jpeg
can’t really tell from the outside if it’s broken. But had it tested and it does in fact was stuck inside.

Awesome!! Thanks for updating the thread for future FitFreaks.

Update: after about 2 fill ups I'm starting to get the check gas cap again which will lead to check engine light soon. My gas mileage I notice as been slowly going back down to 29-31 90% freeway. There seem to still be a leak in the system somewhere and I'm extremely disappointed with my fit. The car only has 35k on it and I baby this car with mobile 1 5k oil change and garage kept plus chevron fuel cleaner once in awhile. The car also struggle on a incline on the freeway, maybe relating to the fuel injector issue. I changed both the purge valve $159 and vent valve $60, what is left to change? The charcoal canister is the only thing left I can think of that will lead to evap leak. Please help with any advise. I'm thinking about just trading the car in and leaving honda.

Have you cleaned your mass air flow sensor with MAF cleaner? I clean all mine once per year when I replace the engine air cleaner. Please be careful and follow these general guidelines:

How to Clean Your MAF SensorNAPA Know How Blog

OMG I never thought about cleaning this. Thank you for the suggestion I will do this over the weekend and hopefully see a difference. I never cleaned it before on this fit but know my old car it made a difference when I got it cleaned. I just thought that this car has low 36k miles I didnt have to touch it. Also I use a K&N recharge filter might be a reason the MAF could get dirty.

Yes indeed the K&N is implicated in early fouling of MAF sensors for several reasons: The OEM air filter (1) doesn't weep K&N filter oil through the air box at high velocities (a), (2) loses it's filtration power of very fine particulates early (larger pore size that the paper filter media), (3) turbulent eddies are formed with the K&N and that throws off the "stable" laminar air velocity that the MAF sensor expects. This is more apparent in sports cars and high output cars that rely on instantaneous MAF reading to deliver instantaneous power demands.

(a) it is imperative that the amount of oil added to the K&N filter be controlled and well distributed.