I bought a Fit a few weeks ago and have now filled the tank up about 8 times. I drive about 700 miles per week. Why when I calculate my mpg it's way different from the dash reading?

ie. Yesterday I filled up (stopped at 1 click) and before driving I reset my tripometer and mpg. I then drove 302 miles and pulled in the next gas station and at that time my dash said I got 36.4 mpg for that trip. I put 9.688 gallons in the tank (stopped at 1 click) and got back in the car.

302/9.688 = 31.17 mpg.

The dash said 36.4 mpg but the true mpg is more like 31.17.

Am I doing something wrong? Is everyone's dash wrong?

Thanks guys!

 

did you by chance purchase an '09? They had incorrect data tables resulting in displaying 10-15% higher avg MPG than actual. There's an ECU reflash that fixes this (dealer should do it for free if they're nice).

Otherwise they tend to be pretty accurate. I'd suspect an issue with the pump shutting off early, however 31mpg seems pretty normal, especially this time of year.

 

Yes, it's an 09. My trip yesterday was all highway (interstate). I was hoping it would get closer to 35 than 31.

 

yah, my 09 was recalibrated at the dealer (just a obd2 flash) a while back. the mpg was like a few miles less.

 

Mine is usually off a little only by 1 or 2mpg no more and been keeping track since new. My MPG thing is almost always right on like that which I am very happy with how accurate mine is.

 

Here is a link to the service bulletin: MPG Calc Fix

Had to have this done on our '09. Note the paragraph concerning out-of-warranty cars and good will.

By the way—the service manager had not heard of this. It was helpful to have a printout with me. No hassle, and it fixed the problem.

Sure have been getting lousy gas mileage this winter. Can't wait for spring.

Cheers.

 

On the other hand, we took a small trip today, 88 miles on freeway at 65 MPH with cruise control on. ('13 Fit 5 M/T) Dash said I got 36 MPG, but the math said 40.12. I guess it goes both ways. I was really surprised to see the MPG reading. We just bought the car Jan 17, used with 3490 miles on it, Base model. I ain't complaining!

Oh, I fill the tank until the nozzle clicks and repeat it each time. I think it gives a fairly accurate reading, just divide miles by gallons.

 

One thing i've never understood is the "nozzle click" and it's accuracy. Everyone is assuming all of these pumps/nozzles are perfect? The way they work is very mechanical. I've had some that never shut off and spilled. Sure the amount of gas that actually comes out is calibrated by Weights and Measures, but what about the nozzle itself? They go through some abuse.

People that fill up to the neck I can't really argue with lol

Not crediting/discrediting anyone, just a thought i've always had.

 

I think the nozzle click is pressure-sensitive, so if you fill really slowly it'll put more gas in (eventually) than if you squeeze the pump all the way and fill it fast.


I think this is the case, but I have no proof... so- experts?

 

yes, pressure. Pressure and magic.

 

Clearly it is magic. It does appear that the shutoff might be consistent. I worked in a gas station for years in my mis-spent youth and had no idea how they worked.

 

Just got a 2010 and MPG display was at 23.4 mpg when I got it. After fill and reset it has been hanging around around 23 to 24 mpg. This seems low. Just give it some time?

 

By 'reset' you mean the trip odometer or disconnecting the battery to reset the computer entirely?
23-24 is low unless you do all stop-and-go driving and gun it between stoplights and it's really hilly where you live and you drive 2 miles and then let it get cold, etc.

 

I meant pressing the trip odometer reset button like one would do after filling up. It sounds like what you are saying, the mpg calculation is an ongoing reading rather than being reset by the trip odo button. Just got this Fit so I still need to RTFM.

 

No, you are correct. Resetting the trip odometer starts the mpg calculation all over again.


Disconnecting the battery resets the computer to determine engine management; some people here say that if the car has been getting different octane gas or driven wildly, then the computer adjusts for that, and if you then operate differently it may take a while for it to readjust. But that's something I'm not that familiar with- I'm sure someone else will explain.

 

Thanks Shaun. BTW I'll find many hours of reading on your website.
I bet you have a few Honda jokes.
My daughter didn't like the manual transmission in the new Honda and said she wouldn't drive it. I said fine, don't have a Fit. My wife said to leave the comedy to others.

 

best pun i've seen since I got here and there's been a few.

 

Happy to help. I have a few car jokes, one Honda joke, and a while back I realized that there are 50,000 words on my website, almost all of them jokes.


That's roughly half a novel.


That's a lot of words...

 

Honda car names lend themselves to puns and groaners.

What do you call an Accord that was rear-ended?

An Accordion.

 

My dash meter is typically a bit optimistic. It usually sits around 42, but I typically get about 38.5.

I drive like grandma, about a 50/50 mix of highway and surface streets.