Yes, the computer is still calculating when you idle. In L.A. traffic you definitely get a chance to witness this.

Yes, I don't get any sleep. Good thing the Fit is fun or else I would sleep at the wheel.

 

There is no easy way to verify that unfortunately.

It was many years ago. The gas company sent us a letter informing of the error in the gas meter. They have been over charging us for few years. The credit paid for the next few months of gas usage.

 

If you're referring to the instantaneous MPG meter not showing any bars at idle, that's because you're getting zero MPG at that time.

 

'06 Civic Hybrid owner here. Looking a lot at the Fit lately for a second car to replace a Jeep Cherokee. In my (wife's) HCH the FCD is off by 1-2mpg, or about 2-4%...only difference here is that it is off in the opposite direction. It will say 51mpg, but calculated is actually closer to 52/53mpg. Which is nice becasue at 50mpg X 12 gal tank (actually 12.4) we can predict a 600 mile tank and not have to worry about the FCD shorting us any miles and running out of gas.

As for how it is calculated, I'm sure it's a correlation of speed and injector opening times. The fuel flows to the engine at a constant rate and normally a fuel pressure regulator sends back unused fuel to the tank. I'd also be willing to bet that an ECU reflash could fix how it calculates.

 

Thanks, that's a new insight (no pun intended) for me. I always assumed they had a flow sensor, but using injector data, which they already have to keep close track of, makes more sense. Cheaper.

I agree, ECU reprogramming will fix this once they find the bug (probably a math error somewhere in the code). I used to be an embedded software engineer for 20 yrs so this is a very interesting topic to me.

If that term is unfamiliar (and this goes for almost anything these days), a quick Google and/or Wiki search will give you the answers ya seek.

 

Just to corroborate what everyone else has reported, I am also consistently seeing about a 4MPG discrepancy between the display and a manual calculation. This includes a 1200 mile road trip (currently halfway through it) driving a combination of highway and back roads.

ifthefoo, by the way - I'm getting about 44MPG average on my '06 Heritage - combination city/highway!

 

That's pretty good! ....... I haven't seen any "hypermiler" discussions pertaining to m/c's... I definitely don't ascribe to such behavior!!

 

Well I finally got my first scan gauge result and it seems that it is only off by 1mpg but I think the recalibration of the fuel tank fill up will make this even more accurate. As for the results at the pump the car avg read 35.9mpg, scangauge read 31 mpg, and hand calculated was 32.1mpg so the scangauge is definitely more accurate and with the ability to calibrate makes it better.

 

We got our car three weeks ago tomorrow and have filled it up a few times and here's what I've seen going by memory.

First fill the computer showed 36 mpg and my calc showed 34+, so I thought it was quite accurate. The next two fills came back with the computer showing 4-5 mpg more than my calculations, consistent with everyone else. I read somewhere that the filler neck can hold a lot of gas, so I wondered if the difference was the dealer initially overfilled the tank and accounted for the higher MPG that first tank.

This past weekend, however, we took the Fit on a weekend Fall road trip, and after the 140 hwy miles + another 120 country/city miles (with a fair amount of stopped traffic with other tourists) the computer reported 43.5 mpg and my calculation showed 41.8 mpg. If the Fit is like other cars I've had, the computer seems most accurate when driving environment is constant (highway) and less so when varied (suburban/country.)

I know with VW/Audi's a person can play with a number in the ECU using a VAG tool to adjust the MPG calculation so it's more accurate. So it would seem only reasonable that Honda could engineer a fix to get more accurate calculations.

 

I hate the MPG indicator. It's always pressuring me! LMAO!

 

Keep in mind I don't have a Fit, but on any car I've never gotten consistent readings on mpg when driving in varied conditions, around town mixed with highway. I do have a 52 mile commute to/from work and when I trek that long distance on the highway, the computer is a lot more accurate. I've maxed out at 35mpg in my GTI, and while it's in the shop I have a loaner Passat with the 2.0 turbo engine, which I averaged 38 mpg with yesterday. I'd really like to believe those numbers, but I know they're a bit optimistic. It does help a lot to stay out of boost though.

 

What are the chances of the dealer trying to put as much gas as possible into the tank?

 

Yesterday while driveing on I-10 I did a test. 09 sports A/T, 40 psi in tires, air on, nice day and 65 mph. I stopped and fill the tank to the top. Drove 106 miles, stopped fill it to the top and it took 2.46 gals. Did the math and it came to 43.08 mpg. The car had 48.4 mpg, thats a 5.32 mpg differences.

 

My latest tank read 38.8 on the gauge and I calc'd 34.8. Exactly 4mpg off. It sounds like most people are getting this same error while a few are getting numbers much closer.

For those getting accurate measurments, what tires came on your car? I have the Dunlops. I wonder if there is a small difference in tire circumference that is causing this? I have also noticed my rpms are higher at 70mph than the theoretical rpms.

 

Note that here in Canada where our readings are L/100 km, I'm consistently calculating 0.7 L/100 km worse mileage than on my car. For example, car said 5.8 L/100 km average and I calculated 6.5 L/100 km. In US MPG that would be 40.6 on the car vs. 36.2 calculated so 4.4 MPG off. Seems consistent between the US and Canadian cars as to the amount the car's computer overestimates the fuel mileage. Hopefully Honda figures out a fix for this! I'd love to have more accurate readings in my car....

My tires are the Dunlop Sport 700....

 

On most of my fill ups I'm getting ~4 mpg difference, yet on some I'm getting less and more. There are many variables to calculating mileage that you just have to look at what mileage you're usually getting if that makes any sense.

 

Don't kid yourself. Yes Honda makes a fine product but they are NOT beyond embellishing a little. I believe the "BSM" is built that way by design. Why, I don't know. Maybe they think that we can't do the math. But this is NOT their 1st attempt at fooling you.

They recently lost a lawsuit because the odometers were reading 5 percent high making you think you were doing better than you were. So they had to fix that, now the BSM reads high instead.

They also had a trip meter that was being "honest" so to speak, so they had it disabled in the name of customer satisfaction. This is built into their navi systems. There have been numerous requests to enable this feature but Honda simply refuses to.

So I doubt Honda will release a flash to correct the BSM or anything else that will make them look worse than they are.

I don't honestly think they get it. We WANT honest reporting from our vehicles! If they really WANT customer dis-satisfaction, just keep feeding us false data and disabling wanted features!!!

Comon Honda! Do the right thing and give us the tools we deserve!!!

 

Interesting. I did read about the odometer class action suit so it appears that even Honda is not above reproach. I really don't get why they wouldn't give customers the tools to accurately monitor their mileage! Well, of course, if I was to belive my car I'd think I was getting better fuel economy than I actually am, I do get THAT. But even being 4 MPG off, it is still excellent mileage. Car manufacturers - I just don't get the way they operate ....

 

Yeah I don't get it. Like the gas gauge illusion. Ever notice you get about 2/3rds of your mileage on the 1st half tank , then it tanks on the last half?

Again an illusion to fool you into thinking you are doing better than you are. If the gas gauge goes down too fast they get lower satisfaction ratings.

Now in Honda's defense they are not the 1st to use this trick. It's now pretty much a standard calibration across the industry.

It just facinates me how the industry uses these things thinking they are really fooling anybody.

The BSM is is consistantly 4 to 5 mpg high. Comon Honda! We figured this trick out in weeks!!!

Want great customer satisfaction ratings? Try being HONEST!!!

 

Make sure to reset the trip mileage meter every tank you've filled. And it'll constant change the avg while in idle. I was chatting with a friend in the car, i saw my avg from 37 drop to 35.5 for 40 mins of chatting