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?

 

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.