In the past year or so mileage on my Honda Fit (08) has decreased at least 100 miles per tank full. Changed spark plugs, put in additive, changed air filter. Tires ok. Suggestions, comments? I have 120,000 miles on it…
How are you determining that its mileage has decreased?
If you can give both numbers (before and after) in miles per gallon, that would help.
Carefully check after driving if any wheel is hotter than the one on the other side. If so, you have a sticking brake.
A new thermostat might not be a bad idea.
Have you changed to a different tire in the past year? Some tires give better fuel economy than others. Have you kept your tires properly inflated all along?
I assume your check-engine light has never come on. You might have an auto parts store scan for codes anyway.
I have an 09 and an 08 Honda Fit. Although the mileage has gone down a little over the years it has not been drastic. How do you know that you are getting a tank’s worth of gas? The gauge may be in error, causing you to fill up more often than usual. You should do a Miles Per Gallon calculation for a few fillups to verify the MPG. Miles per fillup is not accurate in and of itself. Keep track of the miles on the odometer and divide it by the number of gallons you dispense, each fillup. If you are truly getting 100 miles less per tank… what is the MPG you are getting at these fillups. This would have to be your starting point for this evaluation.
Our mileage increased a couple of mpg when I replaced all the Coil Packs. The older Fit’s go thru Coil Packs like crazy due to the old design which retained moisture and corroded. The Fit would occasionally not fire on some cylinders, especially noticeable when the engine was warm and you stopped for a light. The misfire was quite evident. Coil Packs fixed that, now she runs smooth and uses less gas. My '08 Fit does get hit on the gas mileage due to a Thule ski box and 2 Yakima bike racks on top. About 6 mpg less due to racks, but the fun toys need to go on the roof.
Hey, Xena–I just thought you might want to know that you aren’t the only one out there with this problem. My wife and I purchased a used 2007 Fit Sport (automatic transmission) with 103K miles. It runs fine–there’s no hint of it missing–but the mileage is crappy: 22 mpg right now (late January). I’ve changed the plugs and air filter. The tire pressure is fine. The coolant temp is low, but only slightly (172 degrees instead of 175). We typically carry no more than a load of groceries in the car. Our driving is mostly city, but even on a 400 mile highway run earlier in the fall, we only got 30 mpg. (The EPA mileage is 27/35 with an average of 30). The check engine light is off and the car doesn’t have any codes in its record. Bottom line: beats me. --If you’ve found a solution to your problem, please post it. We expect to sell the car if we can’t fix this.
An 8 month old thread-do you really think you are going to get a reply?
"An 8 month old thread-do you really think you are going to get a reply? "
An 8 month old thread-do you really think you are going to get a reply?
CSA
It looks like he’s gotten two replies now… counting this one… 
Probably dragging brakes. My mother-in-law complained of bad gas mileage and when I checked her car…it would not free-roll on level ground. She also needed new brake pads on all four corners.
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