Just bought my '09 Fit three days ago and ran it down to the low fuel alert. Loving it so far!

Quick question: The digital display said I got 37.6 mpg for that first tank of gas. After filling up, my calculations are that it got 34 mpg. Is that discrepancy normal, or will it get closer as the car gets worked in a little?

 

The computer MPG rating is known for having a positive attitude. ~10% difference seems pretty common.

 

it's a permanent feature. ....at least it has been for me through 8000 miles.

 

Interesting....

Do the engineers really think people aren't going to check for themselves and just assume the display is correct?

 

Seems to be the case, yes.

Mine shows probably 10-15% higher than actual every tank.

 

The mileage gauge in the car doesn't take into account fuel used while sitting still or fuel used at start-up. That's where that other 3-5 mpg is going.

 

Actually, it does take into account fuel used while sitting still. Sit at idle (especially soon after you've reset the meter) and just watch the MPGs drop.

 

I've kept track of every drop of gasoline I've put in my car since I got it in January, and came up with some interesting results about a month ago. My experience until then (and since) was about the same as others... gauge running anywhere from 2-5 miles above calculated miles per gallon.

I filled it up last month and hit the highway for a road trip where I was on cruise control at 70-72mph for the great majority of the trip. I ran the tank as low as I could, and got over 400 miles on the tank, averaging over 43mpg. The difference between calculated and gauge mileage was the lowest I have ever seen, and less than 0.5 miles per gallon different.

I guess what I'm thinking is this - the gauge in the Fit is like any other gauge - it takes measurements and averages them over time to come up with a number. When you're hard on the accelerator, you're pulling more gas through the system faster than the gauge can accurately measure. Because of that, the mileage is reading higher than actual fuel consumption calculated once per tank.

Could the gauge be more accurate? Probably. Would it be worth the extra cost? Probably not. We're not flying the shuttle to orbit, or landing an LEM on the moon. We're driving a car across town. Sometimes good enough is good enough.

 

I have a new opinion on this, and I don't think it has ever been mentioned before.

Mine used to be optimistic ehhh roughly 4 mpg.

But after I put lightweight forged wheels on, and the lightweight pulleys....now it is only off by about 2 mpg.

My theory is this........
The program in the MPG Gauge chip is based on the JDM model. Shorter front and rear ends lighter too as no 5 MPH bumpers and maybe the home market model has lighter wheels.

just a suspicion, may or may not be true, but I think it is quite possible.

 

My first fill up, I was told 44.2...I did the math myself and came up with 42...so it wasn't that far off. Either way, I am ecstatic.

 

I don't think so. My car has the short bumpers and I still have the discrepancy. I think it's there to make people who don't check it think they're getting better MPG than they really are.

Of course those of us who know better just get annoyed...

Given that it's worked out on injector cycles there's no excuse.