The MPG reported by my Fit seems to be about 9% to 10% optimistic.

It may show 40, where an actual usage calculation shows 36.5 MPG.

I know this is not state of the art, as my '99 BMW reported consumption to less than 1% accuracy.

What are you results?

 

Yes, my theory has the computer typically at 4 mpg higher than manual calculation. Here's a full thread for ya:

https://www.fitfreak.net/forums/2nd-...ports-yet.html

 

i dont own this device, but use the neutral if your using an auto/sport, can save you up to 30%

 

I think it was CrystalFiveMT who hit it on the nose in another thread, mine has been (so far) consistently +4 mpg over my calculations. So it tells me 36 but my gas-station math (done on my navi-calculator function) tells me 32.

 

holy crud crystal five do you sleep!?

 

i wonder how close the results would be if you hooked up a scangauge too

 

Ahh, maybe his screen name is a clue... JOKING!!!!

 

I certainly hope my electric and gas meters for the house don't overreport by 9 or 10 percent!

 

Yes - it'd be great if someone would do a test comparing SG vs dash vs measured, using some reproduceable test conditions (like the same 100 mile route, speeds, etc). If you can't reproduce the test results, it ain't science. I'd do it but I haven't got a Scanguage. I'm happy enough with my optimisti-gauge. I just subtract 4 (or is it 10 percent?).. I guess at around 40 mpg it's about the same.

 

ITF,

How does the Road King do for MPG?

 

Interestingly enough, just about the same as the Fit - about 35-38 city, 40ish on the highway. Gotta run hi-test (that's 91+ octane) though. I run 87 octane in the Fit and it runs perfectly. I see that Harley has an OBDII port on it's bikes, I wonder what a ScanguageII would show.. I'll have to do some asking around at school and at work.

 

Can honda release new ecu update to fix this issue?

 

I've thought about this. Hopefully the ECU is flash-based (probably is, most modern stuff like that is). In that case the ECU programming could be updated. Hopefully calibrations can be stored as well. I have been wondering where the inaccuracy comes from... Odometer is probably accurate (has to b/c of regulations, but the fuel flow sensor doesn't necessarily need to be. It's kinda weird - Honda engineers a fantastic product, lots of details attended to (just check out the Engine stuff referred to recently on this forum) but strangely, displayed MPG is 10% off? Maybe they're using a cheap fuel flow sensor, or maybe they're adding 10% just b/c they can - no regs to comply to regarding mpg displays... We may just have to mentally be pessimistic by 10% when looking at avg MPG.

 

i think the way the it works is they run an equation for distance travelled and then compute in how much fuel is being used but i dont think it calculates how much load is put on the car when having to climb hills or haul stuff. whats the lowest mpg anyone seen displayed on screen?

 

When you come to a complete stop, it stops calculating. So the difference is all the fuel you burn when stopped.

 

the scangauge has been seen to be +/- 1%

 

Yup, true. It's always about 3 to 4 mpg off (and I've been doing manual calculations against the on-board computer since I got the thing on 09/06/08...same route, same speed, same driving habits).

I'm averaging about 37-38 mpg on hwy, which is anywhere from 2 to 5 mpg higher than advertised.

 

Well, when instantaneous (not average) MPG is displayed, it does use either engine load (or probably - actual fuel being used by the engine as measured by a flow sensor in the fuel line). When the car goes up a hill, that mpg drops pretty substantially, and goes way up when the car does down a hill.

 

Don't undestand that comment... the avg mpg will tick down when you're stopped/idling, meaning it's continuing to do the average calculation (fuel used increasing while miles travelled not).

 

That could be true - I've never seen my avg drop when idling, but that could be b/c I just haven't waited long enough to see a change. I guess if you reset the trip, drove until the avg display first updates, then stop and idle, you might see that. But once you've got 25 or 50 miles on the trip meter, it seems like you'd have to idle an awfully long time to really affect the avg mpg.