Still fairly new around here, but I am worried about my gas mileage.

When I first drove the car it was in the middle of the summer, and there were several threads saying how bad an effect the A/C had on gas mileage.

I was also getting used to the car, and braking on corners that I now steer around without braking.

But my gas mileage has decreased from 30-31 mpg over the first 6 tank fulls (30.35 mpg) to 26-29 mpg over the past 5 tank fulls (28.67 mpg).

My last tank was at least half highway, and half suburban driving, without A/C and still only reached 28.78 mpg.

The mileage started to decrease after I filled it up at a Citgo (1700 miles) and I noticed had ethanol in their gas, but since then I noticed that my other stations have ethanol also, but don't use stickers anymore, but have the warning painted onto their pumps.

Currently I have 3200 miles on the car, and there was another thread saying that carbon deposits were causing bad mileage on another Fit. I usually drive the Fit gingerly and don't wind it up too much, and I am wondering if that is my problem also. Some of the carbon deposit cleaners at the auto store recommend cleaning after 3,000 miles.

Anyone else having this problem or have any suggestions?

The maintenance minder is still at 60% with the original factory oil. I have checked my tire pressure and have them set for 35 which is higher than the 34 I had them set at with the better mileage.

 

Sorry to hear about your issues with the MPG...while reading your post my first thoughts were that you were driving your Fit like a mad man. What's funny about the way I drive mine is that ever since I got it (just over a year ago) I have become completely aware of the way I drive. So, perhaps your "gingerly" is really my "I'm in a friggin hurry" type of driving. Maybe not. BTW, I have averaged 38-39 MPG and have topped out a tank at 41.3 MPG.

One other thing I thought about in your post is where you live...Falls Church, VA. This time of year, the temps are dropping a little bit, so that could explain your recent drop in MPG...mine did the same thing last year. Also, your overall low(er) MPG may be an indicator of overall terrain of where you live. Are there lots of hills? If so, I have found that the Fit suffers poor MPG with lots of hill driving.

Next, go ahead and bump up your all-around tire pressure to 39-40 pounds...you'll be fine. I've noticed it made a huge difference for me.

Finally, last year I started a thread about the K&N high flow drop-in air filter and how it made a small difference in my overall MPG. Just a thought.

These are just thoughts like I said...others may have some ideas to chime in with.

EDIT, I can not make a comment on how A/C effects MPG, as I really haven't seen a big difference. In fact, I seem to get the best MPG in hot summer weather (where I am almost always running the A/C.

 

Blackbeard Seriously doubt carbon is your culprit and would suggest not getting involved w/ those cleaner products. Fit is not really known for carbon issues.

ECU has everything to do with it. It uses your diving profile to manage things. For optimum economy avoid hard, pedal to the floor, acceleration. Equally important is hard braking. Shifting should be in step with what the Fit wants to do. Moderate gas and wait for the revs, then up shift. You can wait for the high revs ifthat's what you're after, but throttle position should be short of full [75%].

Trip profile affects things as well. Short trips are not in favor of long trips. Start and stop driving is the same. Will lower MPG's.

Ethanol in fuel is common these days - don't think it's killing your mileage though.

Check this thread, post #10 has a nice summary, too bad the doc left the house??

https://www.fitfreak.net/forums/eco-...t-physics.html

 

I have an automatic...

But the terrain, etc has remained the same since I purchased the car...

I drive like there is an egg under the pedal that you don't want to break...both for the gas and the brake...

On the highway the speed limit is usually 55 around here, but traffic flows about 5-10 mph faster and that is what I drive at...I am not swerving in and out of traffic, just leisurely keeping up with traffic...

My commute to and from work does not involve any sitting in traffic as my wife's commute to DC does.

My commute is 20-30 minutes each way, and on the way home the highway is usually clear and makes up the first 15 minutes of the commute.

My tach usually is between 1 and 3 on the gauge, rarely up to 4 even...

There seems to be conflicting information as to whether you should put the car in neutral going down big hills or leave it in D...if no one is in front of me I usually put it in N....

I am 48 and have been driving for many years, I have had other cars that were fast, and that bug is out of my system...now I just try and flow with traffic...

Sometimes it seems like the transmission is slipping when going around a corner, then it downshifts and catches...

Put the Garmin in about the time mileage decreased, but doubt it is that big of a draw to influence mpg...

More driving with the lights on as the days getting shorter....

But all things being even, I thought my mileage would increase rather than decrease....

 

Don't know the AT at all. I did see my MPG go up with time. At 3Kmiles I was probably at 35-36. Now I'm seeing 39, not sure what winter will bring. I would say you'll see better at 30% oil life if my intuitions on engine break-in are to be trusted, but they are only intuitions - and mine at that_

 

Dont put it in neutral unless your stopped, Lights and ac/ heater will lower your mpg but not that much usually 10-20 percent from the best. Bad mileage depends on how many short trips. Winter gas comes out next week but that should not matter until it gets colder. I would take it to a dealer and tell them to reset the ecu. I doubt the trans is slipping and I would use better gas, if theres knock it would act like that, it does in my wifes car with 3000 miles on it. I am getting 42 mpg right know and had lights on plus a few cold mornings. When knock happens the ecu retards the timing and not enough power for the trans. The trans dont have enough power to shift and dont know what gear to go in because if knock happens it usually down shifts to rev the motor to stop knock.

 

Yeah, see what your dealer says about it. If I was getting that kind of MPG, I'd be all over my dealer about it.

 

The problem is the dealer dont know, they wont tell use higher octane and if no codes theres nothing wrong. They can reset the ecu and sell you a bottle of fuel injection cleaner but thats as far as they will go. I would fill up with a top tier premium and go for a ride on highway and do a few throttle pass from 45 to 55 or so to clean out the carbon and then if mileage is bad take it to dealer. If car mileage goes up use a top tier gas of your choice but your car might need premium instead of regular. Its not as humid this time of year and octane requirement goes up for a few months until weather get colder. I use premium gas all year long and haven't had any problems and happy with mileage compared to regular.

 

Could it be that they are switching to a different blend of fuel now that the summer driving season is over? I'd be curious how it would look next summer.

My apologies if this seems like pointing out the obvious, but are you carrying anything heavy routinely?

 

Gasoline doesn't change until Oct.15 to semi winter gas. Dec.15 to winter gas and I believe March 15 back to semi summer gas and May15 to summer gas. Every state changes but the south wont have the same winter gas. There is a difference in gas from state to state and brand to brand. A 1 percent additive can change the whole gasoline and effect how it burns. Use a top tier gas and oil and you should not have problems. I use premium because of the additives so I dont have to buy cleaners, mileage is a bonus. I do switch brands too, every 5000 miles because of different additives in the gas. I also like the way the engine runs with premium.

 

In what is in the car. Have had lightweight mat in it to protect cargo area pretty much since it was new. Added winter jacket as I leave from my garage to go to garage at work, just need the jacket if I stop somewhere in between. I doubt it is costing me 3 mpg....

 

If you are letting the pump nozzle click off and calling it a full tank instead of filling to the top, that is probably a reason for the inconsistencies in mileage figures.... I hardly drive my car that I don't hit over 100MPH, wind it to the max in 2nd through 4th gears and seldom got less than 35 MPG and mostly was between 37.5 and 39.0 MPG..... You need to drive it at high RPM and wide open throttle at least some of the time if you ever want it to break in and run well.... It has a rev limiter so you can't hurt it.... I only get a little over 33 MPG now but I put a supercharger kit and some other things on it... It will get as low as 28MPG in stop and go traffic if I am not very easy on the throttle now.

 

I know I don't wind it out very often if at all...

And I am aware of inconsistancies filling the tank...but still the first 6 fill-ups I averaged 30.35 mpg, and the last 5 fill-ups I averaged 28.67, which pretty much rules out the inconsistencies of filling up...

And there is no knocking in the engine...

Pumped tires up to 36 now, that is about as high as I want to go, and 2 psi higher than when I got decent mileage before at 34 psi...

 

Cooler mornings now that warmer weather is fading. Takes the engine a bit longer to warm up. Mine has gone through that drop each fall. Perfectly normal.

 

I'm just doing 22-23 mpg and I'm not complaining anymore... used to be in the high teens only.

 

28-30mpg per tank is about what i've ever gotten; Could be much higher if i was doing all highway driving with no traffic in ideal conditions. But mix of city/highway i've never gotten over 30mpg a tank personally. And it's not like I'm pushing the car up very high rpm either.

 

I am doing a road trip tomorrow (and Friday) and plan on filling up before I leave, and waiting until it is empty again to fill, should be a full tank all highway mileage....

 

i got prety awsome mileages with that low of tire pressure, but i keep mine currently at 50PSI which is the max the tire recommends.. it rides like a freaken rock but i get over 40+ MPG each time i reset the milages for a long trip.

but iam not sure if you want to sacrifice ride quality for MPG. I also have a Cold Air intake... which I would assume make my gas milages even worst, and yet i still have over 40MPG, 41-43 typically.

EDIT: when i mean a rough ride.. i mean it feels like the car has been lowered.. and my suspension is completely stock.

 

If you don't have a sticky caliper or underinflated tires...

Ten to one the motor never broke in, especially being an automatic that will drive without much engine braking. If the rings aren't fully seated, both friction and gaseous leakage will both be higher than normal.

It very well could be carbon buildup, either on the head/piston causing retarded timing or on the topside of the valves causing fuel condensation. Most carbon is built up during cold engine cruise because the dynamic compression and thus temperature is lowest, and the engine metals themselves aren't warm either causing spot cooling in the burn. Once the metals are hot it doesn't seem to form as much, and at heavier loads even in the rich burning conditions the higher compression/temperature will burn it off.

Remember, the cold light going out doesn't mean it's warm; experience with other hondas shows that on an engine I had that warmed up faster than the fit's, the oil didn't get to operating temperature for twenty five minutes in cooler weather, and longer than even that in the winter.

This means if you baby the engine for ten minutes to work everyday you're gonna have massive carbon. I have a family member that killed more than one engine this way. I had the pleasure of driving one of these with 70k babied miles once, it tried to break its motor mounts at 3500 rpm (a four cylinder to boot!) because there was so much carbon on the pistons and sludged oil all through it that the engine went out of balance.

Rule of thumb - if you commute a long ways (~30+ minutes) you really don't have to drive aggressively to keep buildup from happening. It happens, but it's low enough to blow it out without too much throttle, such as a section on a freeway. If it's less distance, it's wise to work in some exercise for the engine depending on the temperatures it's going to see - for example, as I drive 3 miles to work in the morning, I drive a longer loop in the afternoon to get it warmer, and at least a couple few times a week I'll run it hard to get things good and hot. If I don't it really starts to really run badly, with misfires, bucking, trying to stall, etc (as I found out when I tried hypermiling the thing a year ago).

I thought the higher compression of the fit would make it a little more immune, but the doggone thing is so low-friction and the car so light that it warms up slower than any engine I've driven, and with the 173 deg thermostat it doesn't get as hot as almost any other engine, so really it's at a disadvantage.

 

On the way down it was practically in a monsoon Thursday morning/afternoon, with the defroster(thus the A/C), wipers, lights all on, and I am sure there was considerable drag from the pelting rain and loss of traction...but still the mpg gauge read 38.8 when I arrived. Usually travelled about the speed limit or just below as I don't want any out of area tickets. And I used the cruise control...

On the way back there was a slight sprinkle and some rain, but mostly cloudy and clear. By the time I arrived home the gas mpg gauge was about 41.5 mpg. (Would have averaged 44.5 on the way back to bring it up to this number)

Measured mileage after fillup was 40.5 mpg.

I will see what the next fillup brings.

Thanks for your suggestions.