How far has my car actually travelled?

[colric]

Having refueled my TS2 today and checked the MPG I was pleased with the 51.2 av since the last top-up giving an average of 47.86 over the total of 5028 miles covered so far -or so I thought!
I realised for the first time that the mileage shown on Trip A was different to the increase in mileage shown since the last fill up, on the main odometer.
Having recorded both figures since buying the car, I checked back and found a similar pattern but a tendency for the discrepancy to increase.
The odometer I presume is the more accurate therefore Trip A would seem to be consistently over-recording by 3.6 -5.1%.
So my MPG has been worse than I had calculated by around 2 MPG.
Anyone else noticed this?
AND ....Chris our resident technical Guru can you explain this phenomenon for me, especially why the difference is increasing -are the figures measured differently, perhaps Trip A altered by tyre wear reducing rolling wheel diameter?
cheers for any ideas. I will ask the dealer at the first service in mid Sept.
Colric

[Vixon]

Hi Colric, this post just reminded me of an old post of yours regarding the malicous damage.

It must be the Aurora Blue colour that attracts the gits,  my pride and joy, less than a month in my possesion and as well as my little parking scrape which the touch up pen covered really well it now has an attractive white line about 10 inches long down the passengers door. Reported to police and hubby going to either t-cut or touch up pen it this weekend but it really is horrible to know someone gets a kick out of doing this shit.

[colric]

Hi Vixon,
Sorry to hear about your vandalised car.
I have been using T-CUT blue tinted polishing wax to mask the scatches whilst waiting for some more serious damage and a possible all in one deal.
The white undercoat otherwise is clearly visible from yards away.
The mindless Morons will get their dues eventually; it is the way of the world!
Still, I hope you are enjoying driving your car as much as I am mine.
You cannot see the scratches from the inside!
Take care
Colric

[Si]

That's interesting about the difference between the trip and main odometer readings.

I'm a bit of a saddo with this and record every fill up, using Trip A and resetting it each time.  I noticed the other day that my recordings covered about 9200 miles, but the main odometer was on 9600 miles.  Either I've forgotten to record a couple of fill ups (extremely unliklely), or the two readings don't tally waith each other.  From colric's post, I think it has to be the latter.

Without checking my records, I think the average is currently around 43-44mpg.  For the journeys I make I am very happy with this figure.  With my opinion of the car being heavily tainted by the clicking clutch pedal, the mpg figures are probably the main reason why I'm keeping the car at the moment!

[colric]

Hi Si,
Thanks for posting. I am sure the difference between the gauges is an anomaly not just with the Mazda 2 but with other cars, as well.
I am still trying to find out if the figures are measured in different ways.
Sorry to hear you have the pedal box click. 'Stick with it' (sorry I couldn't resist it!) I am sure Mazda will sort it out eventually.
I hope the rest of your car remains reliable and economical to run.
Colric

[Si]

Its unlikely Mazda will ever solve the problem, see my thread here www.mazda2forums.co.uk/forum/index.php/topic,738.0.html.  We are also waiting for the suspension creak to return as that has been "fixed" a few times already. 

As the fuel gauge reads far lower than it is, I guess the trip is configured the same way!

We replaced a year old Yaris to buy one of our 2s, suffice to say that our overall opinion of supposedly wonderful Japanese cars isn't excatly high.  It is reassuring to know that most other owners also have the same niggling little problems with their 2.  The fact that we own two 2s and all the problems occur on both cars, but my wife isn't as sad as me with the mileage/fuel figures!

[colric]

I have had a look on line at topics relating to odometer inaccuracies and both the Society of Motor Manufacturers and the European Commission allow tolerances of + or - 4% in odometer readings - a range of 8%.
This does not explain why odometer and trip readings on the same vehicle, should be different.
In the USA, Honda has settled lawsuits related to the inaccuracy of some of their odometers.
With the Mazda 2's service interval of 12500 miles, a 4% over-reading on an odometer would be 500 miles.
Might be worth pointing this out to a Mazda Dealer if a warranty issue is claimed to be invalidated by an owner exceeding the recommended service interval.
colric