Accuracy of 2015 MPG display?

Eiron · Post by **Eiron** » Wed Sep 30, 2015 9:45 pm

Just curious if anyone has been comparing the accuracy of the 2015 MPG display with Fuelly and/or manual MPG calculations?
I've only tracked two tanks so far, but both were about 10 MPG higher on the Honda display than they were on Fuelly and when calculated manually.

iceman · Post by **iceman** » Wed Sep 30, 2015 10:31 pm

Hi. Since new and ever since, I've found the '15 PCX MPG indication to be very accurate going from 'near the brim' till just after flashing single bar comes on and within a few mpg of the real figures - litres in and trip miles (reset each time). So, the MPG is quite good although I doubt it can ever be %100 accurate owing to sensor location, fuel in each time, position of bike (lean, flatness of where it's parked).
I've got from 127.x mpg (worse case winter fuel and below zero weather) to a best of 147.x mpg (summer fuel and warm weather - some months back). My average since owning the bike May '14 till about 2 weeks ago is 135mpg (on fuelly). If I get 140mpg true (honest figures from litres in/trip), the built in gauge will show me about 135-138) so not bad at all.
The built in gauge is a guide to efficiency of the bike and how it's ridden - it's never going to be completely accurate and I doubt and car/bike had a truly accurate gauge within a few percent. The display, or mine, often goes a bit wild when reset and fuel topped up (very low or very high readings) but soon settles down after a while and gets more accurate as it has more date to go on.

Eiron · Post by **Eiron** » Wed Sep 30, 2015 11:24 pm

Thanks iceman. Maybe I just need more time & more fill-ups to get an accurate trend.
Do you know if the Euro PCX125 & the US PCX150 share the same display & software?

iceman · Post by **iceman** » Thu Oct 01, 2015 1:11 am

Sorry, no I don't. Not sure if the US model shares the same size/shape tank as the 125. Very rarely my MPG gauge has briefly shown 80mpg or once 350+mpg!, but it soon stabilised to a more accurate figure.

My exceptional mpg and great ride is using some of the most convenient to get (for me) and cheapest fuel too - Asda (read walmart) normal unleaded 97 RON fuel (not the super higher RON kind as it's a waste and no better for the PCX despite what some people say).

fantasy2c · Post by **fantasy2c** » Thu Oct 01, 2015 1:25 am

My 2015 us model with 800 miles has averaged around 10mpg higher on the on board computer than hand calculated

honkerman · Post by **honkerman** » Thu Oct 01, 2015 9:29 am

Just a thought...it's possible that the MPG display is set to UK Miles...

I have a similar issue with the counter on my Jag...It counts in UK miles, not US miles.

dkazzed · Post by **dkazzed** » Thu Oct 01, 2015 1:04 pm

There's no such thing as a US or UK mile, it's one mile which is the same.

1 Imperial Gallon however ~ 1.2 US Gallons
1 US Gallon ~ 3.78 litres
1 Imperial Gallon ~ 4.54 litres

honkerman · Post by **honkerman** » Thu Oct 01, 2015 3:54 pm

That's what I meant. Brain had a fart

wojtek_pl · Post by **wojtek_pl** » Fri Oct 02, 2015 2:23 am

My comp is quite accurate. Within 0.1 l/100km .

Bash On! · Post by **Bash On!** » Fri Oct 02, 2015 2:49 pm

You don't think Honda would program it to exaggerate the MPG, do you? Say it ain't so!

I don't sweat the mileage figures, anyway. It's good, it's about 100 US mpg--who cares if it's 101, or 103, or 99, or ....?

you you · Post by **you you** » Fri Oct 02, 2015 3:50 pm

Bash On! wrote:You don't think Honda would program it to exaggerate the MPG, do you? Say it ain't so!

I don't sweat the mileage figures, anyway. It's good, it's about 100 US mpg--who cares if it's 101, or 103, or 99, or ....?

Exactly

Eiron · Post by **Eiron** » Sat Oct 03, 2015 1:20 am

Bash On! wrote:You don't think Honda would program it to exaggerate the MPG, do you? Say it ain't so!
I don't sweat the mileage figures, anyway. It's good, it's about 100 US mpg--who cares if it's 101, or 103, or 99, or ....?

Sorry, but I've come to appreciate Honda's attention to detail. This isn't some marketing wonk getting lazy & using last year's picture in this year's sales brochure. It's Honda's On Board Computer telling me my calculated Miles Per Gallon. Is the speedometer 10% off, too? Or the odometer? They're all controlled by the same computer ....

We're not talking about 2% difference, we're talking about a 10% difference. That's huge.
And, given Honda's reputation for quality & innovation, it's very disappointing.

Eiron · Post by **Eiron** » Sat Oct 03, 2015 1:21 am

fantasy2c wrote:My 2015 us model with 800 miles has averaged around 10mpg higher on the on board computer than hand calculated

Thanks fantasy2c, that helps!

Eiron · Post by **Eiron** » Sat Oct 03, 2015 1:24 am

wojtek_pl wrote:My comp is quite accurate. Within 0.1 l/100km .

Hmmm... another Euro 125 with a precise OBD MPG ...
Thanks wojtek_pl!

gn2 · Post by **gn2** » Sat Oct 03, 2015 6:48 am

Eiron wrote:We're not talking about 2% difference, we're talking about a 10% difference. That's huge.
And, given Honda's reputation for quality & innovation, it's very disappointing.

Honda can't legislate for users failing to fill the tank correctly.
It is perfectly possible for your paper calculations to be correct and for the gauge to be correct at the same time.
User calculations are determined by the amount of fuel added by the user, the gauge accurately measures the amount of fuel injected into the engine.

iceman · Post by **iceman** » Sat Oct 03, 2015 7:01 am

gn2 wrote:
Eiron wrote:We're not talking about 2% difference, we're talking about a 10% difference. That's huge.
And, given Honda's reputation for quality & innovation, it's very disappointing.
Honda can't legislate for users failing to fill the tank correctly.
It is perfectly possible for your paper calculations to be correct and for the gauge to be correct at the same time.
User calculations are determined by the amount of fuel added by the user, the gauge accurately measures the amount of fuel injected into the engine.

Everything so far indicates UK/EU ones seem to be in agreement give or take a small amount and all reported US ones out by a big margin - how does that tie-in with 'users failing to fill the tank correctly' other than some difference across seas. If users reset the trip each time, add a known amount of fuel and cover large distances between fill-ups then that is an accurate way to say how many mpg is used.

gn2 · Post by **gn2** » Sat Oct 03, 2015 8:07 am

US ones being out could be down to a difference in units.

honkerman · Post by **honkerman** » Sat Oct 03, 2015 8:26 am

Exactly what I was trying to say gn2. It's probably reading in UK gallons, which my Jag also seems to do. It makes sense as the 125 and 150 most likely share the same electronics (no poiint in engineering something different for such similar bikes), and the lions share of pcxs aren't sold in the U.S..

Eiron · Post by **Eiron** » Sat Oct 03, 2015 2:26 pm

gn2 wrote:Honda can't legislate for users failing to fill the tank correctly.
It is perfectly possible for your paper calculations to be correct and for the gauge to be correct at the same time.
User calculations are determined by the amount of fuel added by the user, the gauge accurately measures the amount of fuel injected into the engine.

Uh .... thanks?

Yes, I started by saying that I've only run thru 2 tanks (approx 400 miles) so far. I admitted (before I finished my question) that I'm basing my question on limited data. I'm going to keep track, but my initial calculations had me curious.

Also, if it were a US Gallon vs Imperial Gallon difference, it would be a 20% MPG difference!

iceman · Post by **iceman** » Sat Oct 03, 2015 2:40 pm

What if you have the meter set to km/litres (mine came set to km/litres or something like that so I changed it). Not sure if that makes things more accurate and may be a pain to get used to

- still strange Honda cannot correct the s/w or such to make bikes sold in different countries read correctly.

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Accuracy of 2015 MPG display?

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