Hello fit forum
Ive been trying to "recondition" a used 2011 fit sport with unknown maintenance history and 147000 miles.
Used cars are at a premium price these days, Fits are renowned for good mileage. I need the space it has, and all around think its been a damn good choice!
BUT
Mine gets 22 avg mpg. Reset on the ecu brings it back to 36-40 mpg, then it settles back to 22 mpg.
My best guess is one of the sensors is giving it bad info, anyone familiar with this problem?
Best,
David

 

Couple questions:
1) Are these mpg averages calculated over a full tank of fuel? Multiple tanks?
2) Are these mpgs calculated "at the pump" or are these the numbers you see on the dash readout?
3) Are your driving conditions the same when you report 22 mpg vs 36-40 mpg?
4) Does the car feel different after resetting the ECU? Smoother? MOAR POWR?

I have a hard time imagining a scenario where you could get 22 mpg on one tank and 36-40 mpg on another tank without doing something drastically different (e.g., auditioning for the next Fast and Furious movie). I also can't imagine how a bad sensor could cause that sort of mpg swing without clear and obvious changes in overall performance and driveability. Hopefully someone else will have direct personal experience with this sort of situation.

Just for reference, I have a 2010 Sport AT with just over 100K miles. I average 40-42 mpg ("at the pump") on long highway drives and 35-37 mpg if most of the tank is used for short/city/winter driving. I drive carefully, never speed, and coast down hills and to lights. The average mpg value shown on the dash display varies more than this, and I have had full tanks where the dash display was both optimistic and pessimistic by up to 4-5 mpg vs the pump calculation. Note that I don't know if any dash display correction was ever done on my Fit prior to me getting it about a year ago.

As soon as my wife jumps into the Fit the dash display starts dropping, and the tank average calculated at the pump is also lower. Maybe 30-34 mpg if she drives for a whole tank, even on the highway. She is also a careful driver but she doesn't pay as much attention to gentle throttle application and manipulation during acceleration and while cruising at a steady speed and doesn't anticipate conditions as far ahead to allow for more coasting.

So, in my experience different driving styles will net quite different fuel efficiency in an AT Fit Sport, but I can't imagine getting 22 mpg over a full tank in any driving scenario I have ever experienced.

 

I'm no mechanic, but I'd be looking at O2 sensors first. Checking the plugs might show you if it's running real rich. What have you done so far to fix it up?