Author Topic: What MPG are you getting from your Honda Jazz ?  (Read 175520 times)

guest6644

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Re: What MPG are you getting from your Honda Jazz ?
« Reply #120 on: April 28, 2017, 05:35:36 AM »
43 mpg

2008 Mk 2 GE8 Honda Fit RS (Japan).

Hong Kong, city driving approximately 6-7 miles each trip, with aircon.

195/50r16 tires means they're slightly smaller than the standard wheels that came with the car, so I believe the mpg figure the computer gives is less than actual.

guest6040

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Re: What MPG are you getting from your Honda Jazz ?
« Reply #121 on: May 01, 2017, 02:05:47 AM »
We just completed a 3,535km tour of central South Island, NZ in our 2013 Jazz Sport, 1.6l. For the whole 12 days we averaged 6.4l/100km = 44.1376mpg.I used Cruise control most of the time to avoid exceeding 104 kph (upper limit for the Cops), but occasionally drifted to 120 kph when passing MPVs & on some of the wide open straights. A lot of the roads were winding, and sometimes steep, especially to & from Milford Sound. I came in under budget for fuel costs subsequently ! ;D 8)

peteo48

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Re: What MPG are you getting from your Honda Jazz ?
« Reply #122 on: May 31, 2017, 04:05:13 PM »
I have almost done 4,000 miles in my current Jazz. Manual calculation of mpg (I have kept Trip B constant since getting the car) is 44.1 - the computer says 48.4.

So, over 4000 miles, the onboard computer is 10% out almost exactly.

I found this on my previous Jazz, my Civic and a VW Golf - 10% seems to be the discrepancy over a reasonable period with most of these gizmos. It varies from tank to tank but over a period - 10% is the figure.

Yes it would nice if they gave an accurate figure but I can work with 10% - tempted to ditch my manual calculations which I do on Fuelly.com except I'd miss the graphs and pie charts!
« Last Edit: May 31, 2017, 04:06:54 PM by peteo48 »

guest6425

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Re: What MPG are you getting from your Honda Jazz ?
« Reply #123 on: May 31, 2017, 04:13:02 PM »
10% is coincidentally the amount held in the reserve, I've discovered an average of 8-9% out

I've also noticed that now it's warmer I seem to  be getting lower MPG (it's not air-con as that's on all year round)

Jocko

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Re: What MPG are you getting from your Honda Jazz ?
« Reply #124 on: May 31, 2017, 04:38:05 PM »
My MPG has improved dramatically since the warmer weather has arrived. I don't have Air Con. Perhaps it is the warmer weather puts a greater load on the Air Con in the summer, and that extra load has to pull energy from somewhere.

peteo48

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Re: What MPG are you getting from your Honda Jazz ?
« Reply #125 on: June 01, 2017, 10:44:12 AM »
The other thing I've noticed is 44.1 is the mpg attained over a type of driving that is 50% city and 50% highway. I had to do a lengthy commute of 70 miles a day for a month last year and that has boosted my highway figure. I suspect my mpg will gradually fall back to about 40 which was what I got from my previous Jazz doing 80% city driving.

peteo48

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Re: What MPG are you getting from your Honda Jazz ?
« Reply #126 on: June 01, 2017, 10:47:01 AM »
10% is coincidentally the amount held in the reserve, I've discovered an average of 8-9% out

I've also noticed that now it's warmer I seem to  be getting lower MPG (it's not air-con as that's on all year round)

Actually I think 9% might be my figure to be strictly accurate. 91% of 48.4 gives just over 44.

Always assuming I'm doing it the right way round!

guest6827

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Re: What MPG are you getting from your Honda Jazz ?
« Reply #127 on: June 02, 2017, 08:41:15 AM »
That's interesting about the trip comp

Ours says avg 44.something. Most of our miles are urban.

peteo48

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Re: What MPG are you getting from your Honda Jazz ?
« Reply #128 on: June 02, 2017, 12:32:37 PM »
It's interesting Medley but I've noticed this 9 to 10% discrepancy on 4 different cars although 3 were Hondas. Every now and then you'd get an odd reading that was outside of that 10% range - either over or under but over the long haul 9 to 10% seems about right.

On various forums I've seen claims that the computer is only slightly out but I am sceptical. That doesn't mean the computer reading is useless - far from it - but they tend to underestimate the amount of fuel used.

Jocko

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Re: What MPG are you getting from your Honda Jazz ?
« Reply #129 on: June 02, 2017, 08:42:00 PM »
I had a funny today. I topped up my tank at about a quarter full (I had a long journey and wanted a full tank before I started out). Display was showing 57 mpg so I expected to find it was around 55 (usual error). However, the calculated value was 50. I then noticed that I had put in 7.5 gallon, which is about what I get in from the fuel light first flashing (I stop at the first click off). I can only assume that the pump didn't click off when I expected and I managed to fill the neck. I'll see what happens at the next top up.

peteo48

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Re: What MPG are you getting from your Honda Jazz ?
« Reply #130 on: June 03, 2017, 04:56:56 PM »
Interesting Jocko. I stop at shut off but this must vary from tankful to tankful, from pump to pump and even from the pressure you apply when pumping.

It's why a true picture is only gained over several tanks.

pb82gh3

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Re: What MPG are you getting from your Honda Jazz ?
« Reply #131 on: June 03, 2017, 06:15:33 PM »
After 9 months ownership my Mark 2 Jazz Si 1.4 bought with 10000 miles on the clock has done 50/50 city/long distance driving. Most of the city drives are very short. My overall mpg is 39.7, single fill up best 50.76, worst 31.68 (when I first had it).
I'll have to try harder to meet the 47.9 quoted on Honest John's Real MPG website

peteo48

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Re: What MPG are you getting from your Honda Jazz ?
« Reply #132 on: June 03, 2017, 09:42:02 PM »
As regards Honest John's website I think I'm right in thinking he asks people to submit readings from the car's computer as opposed to brim to brim manual method. This is inherently inaccurate as the computers are almost always about 10% out (give or take).

So I'd take the 47.9 figure with a big pinch of salt - it'll be nearer 42 in real life.

pb82gh3

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Re: What MPG are you getting from your Honda Jazz ?
« Reply #133 on: June 04, 2017, 03:48:35 AM »
My method is brim to brim so I feel a little better about my mpg now, thanks.

culzean

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Re: What MPG are you getting from your Honda Jazz ?
« Reply #134 on: June 04, 2017, 09:40:10 AM »
To check how your driving style is affecting fuel consumption you really need to keep zeroing the trip,  from zero to about 50 miles traveled the average fuel consumption reading  is very sensitive to instantaneous fuel consumption, but after that it gets bogged down and slow to react as is averages out the instantaneous consumption over the miles traveled on trip.  This averaging slows down its reaction and in the end after about 100 miles the average mpg barely reacts to whether you are coasting downhill or climbing up mount Snowdon.

The MPG readout gets the fuel used data from injector open time (from ECU) and the miles traveled from the trip / speedometer - the Speedometer is normally calibrated to read 'fast' to make sure you don't get caught by speed camera etc.  so the car actually thinks it is going faster than it is (and covering more miles for petrol used) this 'safety margin' accounts for some of the 'optimistic error' in mpg readout.
« Last Edit: June 04, 2017, 10:46:44 AM by culzean »
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