1.4 fuel economy town driving mostly

[guest5040]

My trip computer is about 10% optimistic as I can check it against my inputs on Spritmonitor. Had a look at my car manual and cannot see a way of changing from miles per litre (presumably as you would be mixing an imperial measurement with a metric one).

[guest4629]

And Halden hill doesn't help. I never "gain" the mpg i lost going up when going down ...,if you see what I mean, and the roadwork holdups don't help either.

[Eddie Honda]

1. Out of interest how accurate have people found the Jazz's trip computers mpg statements when compared to actual mileage/gallon? (My previous Legend was hopeless)

So far based on 21 full tanks:
15% of the time I get more mpg than the computer (computer is 1% to 5% under my figure)
5% of the time I get the same mpg as the computer
80% of the time I get less mpg than the computer (computer is 1% to 16% over my figure)

of that 80% the computer is on average about 7.6% optimistic.

2. Is there  a configuration that you can change to get it to read out in Miles per Litre?

Yes, it's called finishing the very long process called metrication. 

Convert your litres into Imperial gallons and use mpg. Alternatively convert your miles into kilometres and use L/100km. Mixing Imperial and SI units?    Arrrrrggghhh!

[applicationcen]

so from a max brim to a max brim'd tank

Real World Calculations

101.1 miles
15.79 litres
29.13 MPG

Honda Computer
30 MPG

[madasafish]

Over 11,000 miles..

Real world (Fuelly) 43.0mpg

Trip :48mpg.

Been the same overoptimism  since new.

Any figures based on less than 5,000 miles are likely to be significantly affected by special factors ...

[Eddie Honda]

Real world (Spritmonitor)

18,597km (11,556 miles) / average 6.2 L/100km (45.6 mpg Imperial / 37.9 mpg US)

[Eddie Honda]

Real world (Spritmonitor)

18,597km (11,556 miles) / average 6.2 L/100km (45.6 mpg Imperial / 37.9 mpg US)

madasafish, I make your trip comp 11.6% over-optimistic. I found your Fuelly. Is there no way yet to shoehorn it into your sig or profile? http://www.fuelly.com/car/honda/jazz/2012/madasafish/239192

[peteo48]

Over 11,000 miles..

Real world (Fuelly) 43.0mpg

Trip :48mpg.

Been the same overoptimism  since new.

Any figures based on less than 5,000 miles are likely to be significantly affected by special factors ...

5 mpg out. Pretty similar to mine. It's 10 - 11% optimistic virtually all the time.

[degzi]

Get the little thing in as high a gear as possible. If the roads are flat you can still get into the 40 mpg ranges. I'm regularly in 4th just letting it virtually tick over. Just don't let engine labour and your fine.

[lexi]

  The average 56mpg diesel car drops to 38mpg in the city too.
   My petrol v6 will drop to 16mpg in that kind of driving.  I try and avoid it as it does an easy 34 mpg on country roads.
               This Jazz indicates an overall 47mpg on it's town motorway driving. Not done accurate yet.

[peteo48]

Of course, and this applies to all cars, the "official" mpg figures are almost completely unattainable in any real life situation. "Which" reckon that the combined figure is around an average of 19% optimistic.

So I always regarded the 51 mpg figure as strictly for the birds. My overall average of 41.3, given 80% city or urban type driving is one I am pretty satisfied with on the whole.

I just can't imagine how you would get 51 mpg. I guess a steady drive, at 50 mph, on the motorway on a warm day might just do it.

[culzean]

Of course, and this applies to all cars, the "official" mpg figures are almost completely unattainable in any real life situation. "Which" reckon that the combined figure is around an average of 19% optimistic.

So I always regarded the 51 mpg figure as strictly for the birds. My overall average of 41.3, given 80% city or urban type driving is one I am pretty satisfied with on the whole.

I just can't imagine how you would get 51 mpg. I guess a steady drive, at 50 mph, on the motorway on a warm day might just do it.

if you look at the TV ads for cars now there is a disclaimer at the bottom of screen (mostly unreadable as they normally are) saying 'mpg figures may not be attainable under real driving conditions and are only intended for comparison between vehicles' - says it all really - manufactures know it is a load of bulls##t and they may not have to prove it so they put down some outrageous figures.  BTW the mpg figures supplied by Honda are acknowledged by most websites to be the most accurate of all the manufacturers - at over 90% achievable - don't know where the others get theirs from - maybe the old and trusted method of thinking of a number, double it etc. etc.

I have found that the more smoothly (I didn't say slower) you drive the closer the trip mpg figure matches to actual mpg. Seems that by taking the peaks and troughs out of the fuel flow makes the reading more accurate - seems that most ECU's use the injector 'on' time to calculate mpg.

[VicW]

  BTW the mpg figures supplied by Honda are acknowledged by most websites to be the most accurate of all the manufacturers - at over 90% achievable - don't know where the others get theirs from - maybe the old and trusted method of thinking of a number, double it etc. etc.

The figures are achieved by testing in accordance with a government devised test procedure that enables the cars to be run under ideal conditions. So there is no provision made for cold starts, varying traffic conditions etc.
This to be changed to a more realistic test next year I believe.

Vic.

[peteo48]

I have found that the more smoothly (I didn't say slower) you drive the closer the trip mpg figure matches to actual mpg. Seems that by taking the peaks and troughs out of the fuel flow makes the reading more accurate - seems that most ECU's use the injector 'on' time to calculate mpg.

That's interesting and actually makes sense to my admittedly unscientific brain.

Saying that, given that I know the computer is 5 mpg (give or take) optimistic I can use it to make an educated guess as to what my mpg will be at next fill up. It's only my inner nerd that keeps me doing the fuelly.com entries (backed up by my own manual record of brim to brim fuel ups).

[applicationcen]

The petro related downstream industries as well as car manufacturers would have us all driving around in 1920's unsafe and thirsty technology if their investors and government lobby companies and legal advisers got it their way all the time.

Occasionally a good idea comes up like - erm Safety or Efficiency. Then it is a case of who can waterdown or twist market advantage to the most from what used to be a good idea.