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Honda Jazz Forums => Honda Jazz Mk2 2008-2015 => Topic started by: guest7173 on December 16, 2017, 12:37:50 AM

Title: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: guest7173 on December 16, 2017, 12:37:50 AM
Got 29 mpg in 100% urban environment with all traffic jams. Tyres pressure is OK, eco button is on, brakes do not overheat (so no unwanted contact with disks), dashboard lighting is green, not blue most of the time, I accelerate and decelerate slowly but still 29 mpg. Is this normal or what are the obvious things to to check?

EDIT: The gearbox is CVT.
Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: Pumpkin on December 16, 2017, 01:23:09 AM
I'd say it's normal. I drive 50/50 on urban and fast roads and I get 38mpg, although mine is an auto.
Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: guest5770 on December 16, 2017, 08:00:59 AM
Auto or manual, lots of short journeys?
The fuel consumption of my CVT goes up dramatically as the temperature drops, especially on short journeys.
Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: guest7173 on December 16, 2017, 08:52:14 AM
Auto or manual, lots of short journeys?
CVT and average journey is couple of miles.
Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: Jocko on December 16, 2017, 09:17:12 AM
I have a ScanGauge fitted to my Mk1, and what you are getting is similar to what I see during short urban journeys, at this time of the year.
Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: d2d4j on December 16, 2017, 09:20:02 AM
Hi

I hope you don’t mind, but having read j@zzy post, I have a question

Does the dashboard lights change colour depending on how you drive

It’s just jazzy stated dashboard lights are green and not blue

Many thanks

John
Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: Jocko on December 16, 2017, 10:27:14 AM
The 67 plate Jazz I had on loan had a section of the dashboard which lit up a different colour depending on how I was driving. Assume it is an eco monitor.
Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: Kenneve on December 16, 2017, 10:41:23 AM
I can confirm that (on a Mk3 EX)  the lights do indeed change from green to blue, depending on your style of driving.
Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: trebor1652 on December 16, 2017, 11:15:31 AM
Yes modern day version of a vacuum guage.

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Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: peteo48 on December 16, 2017, 01:56:38 PM
My record low is 33.8 over around 250 miles (when I normally refuel). At points I reckon my consumption will have dipped below 30 mpg  and is only balanced out by a few longer trips.

The old boy across the road from me reckons he hasn't seen 30 mpg for years! He has a 1.8 Civic which replaced a 1.6 Focus. He rarely does more than 3 miles a day all in town traffic.

PS

Above figure "achieved" in winter.
Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: madasafish on December 16, 2017, 02:00:40 PM
My average urban is 42mpg . BUT my average journey is 6-10 miles.

On cold weather and 2 mile journeys, then 32mpg..at most
Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: Jocko on December 17, 2017, 04:41:29 PM
Today, I covered 100 miles on mainly dual carriageways, wet roads, temperature about 6°C, two up. According to my ScanGauge E, I averaged 49.3 mpg, but on level roads, light throttle, and 40 - 50 mph, I was struggling to get the instantaneous mpg above 35. I was using my best hypermiling techniques, with little success. It is like driving through treacle. Wet roads and cold tyres are the death of fuel efficiency. 29 mpg in urban traffic and with short trips is pretty good at this time of the year.
Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: peteo48 on December 17, 2017, 05:50:48 PM
The other thing I would mention is how different in this respect petrol cars are to diesels. My 2 diesels - both VW 1.9 TDIs didn't show the same swings from summer to winter. A low of about 45 mpg in the winter (tank to tank) going up to about 52 mpg in the summer. As I said above my lowest in a Jazz has been 33.8 over a tank but I did get 56.2 in May last year so nearly 23 mpg difference.
Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: Jocko on December 17, 2017, 06:05:19 PM
The figure shown below my avatar is my average mpg figure since buying the car, 18 months ago, courtesy of www.spritmonitor.de where I record my mileage figures.
Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: rogbro on December 18, 2017, 09:08:10 PM
Wow!!! I don't think that's very good MPG for a Jazz.   Our last car, Mini coopers S,  200+ bhp returned 28 mpg urban
Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: guest7173 on December 24, 2017, 02:18:00 PM
Is there any way to improve mpg in winter time?
Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: culzean on December 24, 2017, 02:36:28 PM
Is there any way to improve mpg in winter time?

The only way to use less fuel in winter is not to drive so much (technically this is not improving mpg because no miles / travel involved) .

To allow engine to warm up faster drive off as soon as engine is started, letting a cold engine idle on your drive means slow warm up and wasted fuel.  Using the heater can mean slower engine warm up so wear a fleece and glove and don't use heater  (like many BEV drivers do)..   Do the normal fuel saving stuff like using brakes as little as possible, change up early, don't accelerate any faster than you need to (rapid acceleration drinks fuel). Make sure tyre pressure is correct to lower rolling resistance.
Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: Jocko on December 24, 2017, 02:54:32 PM
I don't put my heater on (control in the blue) until the engine warms up. This allows the blue light to go out a quarter mile earlier than if the heater control was set to red. Another thing I have been advised to do, but have never got around to trying, is to block the lower grill. Something not too permanent so it can be easily removed when the weather warms up. I have a a ScanGauge E fitted so I can actually monitor the coolant and intake air temperature.
I keep my tyre pressures 3 or 4 psi over Honda's recommended figures. I also check my tyre pressures on a weekly basis (always checking and adjusting them when cold).
Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: madasafish on December 24, 2017, 06:23:26 PM
Don't accelerate hard when engine is cold.
Try not to drive up hills when engine is cold.
Brake little when engine is cold.
Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: eagle123 on January 10, 2018, 02:52:33 PM
Don't accelerate hard when engine is cold.
Try not to drive up hills when engine is cold.
Brake little when engine is cold.
Make sure you fill up half a tank and declutter your car take excess weight off correct oil check tyre pressure change to eco tyres drive smoothly anticipate ahead


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Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: culzean on January 10, 2018, 04:09:50 PM

Make sure you fill up half a tank


With the Jazz weighing 1100 Kg saving weight of half a tank of fuel (less than 20kg) is hardly going to make any measurable difference,  in any case I try never to let my tank get less than half empty because without fuel a car is just an expensive ornament. 

A fast warmup and avoiding using brakes,  avoiding excessive acceleration and speed above 50 if possible will give best payback.

Most engines do less than 20mpg until they warm up, and with short journeys your car never gets warm.  Suggest you zero the trip and take it for a decent run (more than 20 to 30 miles) driving carefully and see how the consumption goes.  It is important to zero the trip (I do it every time I fill up) because the mpg indication is at its most accurate and sensitive when trip at zero,  as the miles build up on trip it gets very sluggish to change and after about 100 miles mpg readout hardly changes whether you are going downhill,  uphill driving carefully or not.  This effect is because the fuel usage data (the injector open time taken from ECU) is averaged out over the total miles on the trip and as the miles build up and change in instantaneous fuel usage is swamped by averaging it over more miles.   The mpg readout normally updates about every 10 seconds.


In fact if you zero the trip from cold and drive say 5 miles you will see 'cold mpg' if you then zero trip with engine warmed up you should see a marked difference in mpg.  Winter is not a good time to check MPG as the results are normally disappointing.
Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: Jocko on January 10, 2018, 06:08:33 PM
I always fill my tank to full. Until the first click off of the pump. The only way to get an accurate mpg figure is to fill the tank, zero the trip (or note the mileage - I do both), refill tank when fuel light comes on. Divide the miles covered by the gallons added to fill tank, and there is your mpg figure.
Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: peteo48 on January 10, 2018, 08:20:16 PM
I do the same Jocko. Only difference is I tend to refuel when the miles left "guessometer" reaches gets down to 100. Don't like living on the edge lol (probably why I haven't bought an EV yet!)
Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: Jocko on January 10, 2018, 08:46:36 PM
My dashboard display just shows Average mpg. My ScanGauge shows anything I want! If there is any likelihood of a longer run I will fill up earlier, but my local filling stations are 24 hour so if I got an urgent call in the middle of the night, I can get petrol.
Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: John Ratsey on January 11, 2018, 09:02:48 AM
Short trips, particularly in the winter, are a killer for decent fuel economy. My HR-V has a trip computer display option which shows the mpg for the current trip and it's informative to watch the number increase as the journey gets longer. It takes at least 5 miles (and maybe nearer 10 miles) in the winter for the engine to warm up properly and reach full efficiency. I always knew that efficiency and economy dropped but seeing the numbers on a screen has highlighted the extent.

I've considered, but not implemented, half blocking the front grille during the winter months in order to help with the warming up. I'm surprised that manufacturers don't provide thermostatic louvres but they lack the incentive as the standard tests don't include winter fuel economy.
Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: Jocko on January 11, 2018, 09:40:52 AM
I keep meaning to block the lower grill for just that very reason. It takes almost 10 miles before my average mpg starts to recover after a winter start. And the majority of my daily journeys are less than 4 miles. The ScanGauge is great because I can customise the display to show a variety of data while it shows a graph of running mpg around the current average,
(http://www.scangauge.sk/wp-content/uploads/2013/02/header_scangauge-e.jpg)
Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: eagle123 on January 11, 2018, 10:15:36 AM
I keep meaning to block the lower grill for just that very reason. It takes almost 10 miles before my average mpg starts to recover after a winter start. And the majority of my daily journeys are less than 4 miles. The ScanGauge is great because I can customise the display to show a variety of data while it shows a graph of running mpg around the current average,
(http://www.scangauge.sk/wp-content/uploads/2013/02/header_scangauge-e.jpg)
Petrol cars aren't that efficient due to their Otto cycle deisels burn more efficiently and are relatively 30 percent more efficient.
A interesting recent design by Mazda for their new sky active X engine marries both deisel and petrol advantages. It uses variable combustion cycles to mimic petrol smooth running to dedeil like torque and exonmy.


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Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: culzean on January 11, 2018, 11:21:25 AM
Petrol cars aren't that efficient due to their Otto cycle deisels burn more efficiently and are relatively 30 percent more efficient.
A interesting recent design by Mazda for their new sky active X engine marries both deisel and petrol advantages. It uses variable combustion cycles to mimic petrol smooth running to dedeil like torque and exonmy.


If you take away the fact that Diesel fuel is heavier than petrol and contains about 20% more energy per litre it explains 'diesel efficiency' a bit LOL  - IMHO because of higher energy diesel should actually be 20% more expensive than petrol, also  a standard barrel of crude yields on average 20 gallons of petrol and only about 9 of diesel, another reason to raise diesel price, there is less of it.

The Mazda 'petrol-Diesel' direct injection is very interesting, my brother has new 1.4 Skoda  with similar technology and is very happy with its mpg.
Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: Jocko on January 11, 2018, 11:34:20 AM
The Mazda 3 with Its Skyactiv-X Compression-Ignition Gas Engine is actually a petrol engine.
Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: guest5079 on January 11, 2018, 02:20:47 PM
Whilst this is a deviation from the query, much to the chagrin of some, my favourite couple opposite have an Audi and a Ford van. Dumber as I call the female ( this is what my Wife has  observed previously) comes out in pyjamas and starts the Audi ( diesel), this morning the headlights were shining into our bedroom so I timed her. 18 minutes between starting the car and driving off.  Not only an offence but as I used to tell motorist when I caught them leaving a car running while they went into a shop. If it gets stolen, you will have to go and collect it and the chances are your Insurers will not pay out for anything. At 30mph this Audi could be 7 miles away before she comes out. The van has not been taxed for some considerable time.
It might be a diesel but over a week I should think a fair bit of fuel is wasted not withstanding the pollution.
Does anyone know if the Audi is fitted with the very expensive 'particulate filter?' which I believe loves this sort of treatment.
Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: guest1372 on January 11, 2018, 03:32:58 PM
Does anyone know if the Audi is fitted with the very expensive 'particulate filter?' which I believe loves this sort of treatment.
At the risk of increasing your blood pressure any further, probably this one has been removed and had a 12mm drill bit put through several times as an 'improvement'.
--
TG
Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: guest1372 on January 11, 2018, 04:11:46 PM
With the Jazz weighing 1100 Kg saving weight of half a tank of fuel (less than 20kg) is hardly going to make any measurable difference.....
I think I demonstrated the maths for this a while ago, at low speed it does not matter but at higher speed the energy required to accelerate a mass is definitely a reason to save weight.

It takes 14x more energy to accelerate a mass from 65 to 75mph than from 0 to 10 mph.  The extra 20kg subjected to a varying speed wastes energy.  It takes ~200 Joules to lift 20 kg by 1 meter, it takes ~3000 J to accelerate that mass from 65 to 75 mph.  This has nothing to do with drag, these figures would be the same in a vacuum.  Carrying the unused half of your tank around is like lifting a 20kg bag of sand into your boot 15 times every time your speed increases 10mph on the motorway.  Of course this is where cruise control wins.
--
TG

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Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: culzean on January 11, 2018, 04:43:34 PM
With the Jazz weighing 1100 Kg saving weight of half a tank of fuel (less than 20kg) is hardly going to make any measurable difference.....
I think I demonstrated the maths for this a while ago, at low speed it does not matter but at higher speed the energy required to accelerate a mass is definitely a reason to save weight.

It takes 14x more energy to accelerate a mass from 65 to 75mph than from 0 to 10 mph.  The extra 20kg subjected to a varying speed wastes energy.  It takes ~200 Joules to lift 20 kg by 1 meter, it takes ~3000 J to accelerate that mass from 65 to 75 mph.  This has nothing to do with drag, these figures would be the same in a vacuum.  Carrying the unused half of your tank around is like lifting a 20kg bag of sand into your boot 15 times every time your speed increases 10mph on the motorway.  Of course this is where cruise control wins.
--
TG

The OP did say that he only does very short Urban (presumably low speed journeys if he wants to keep his licence).

Most people (including RAC and Honest John) agree that cruise control is OK on the flat but on both up and down gradients can make fuel consumption worse.
Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: applicationcen on January 11, 2018, 05:18:45 PM

From a semi-auto iShift point of view 29 mpg is a bit low even in demanding urban.

From a CVT point of view people recognise CVTs do not quite hit the same efficiency as a manual.

29 is very much in the broad range one might expect so it is unlikely there is anything wrong with the car, assuming you are topping up your lubes & fluids at service times.

Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: eagle123 on January 11, 2018, 07:31:23 PM

From a semi-auto iShift point of view 29 mpg is a bit low even in demanding urban.

From a CVT point of view people recognise CVTs do not quite hit the same efficiency as a manual.

29 is very much in the broad range one might expect so it is unlikely there is anything wrong with the car, assuming you are topping up your lubes & fluids at service times.
True it is low wondering if the fuel consumption has improved compared to cars of the 90s as doing short journeys my mark one jazz was averaging like 32 mpg in winter these were short start stop journeys.
I had a 1.4 petrol astra 1994 with a high torque engine the fuel consumption was similar.

Driving style maintaining the car using genuine parts the correct oils does affect fuel econmy.

The most I had on my mk 1 jazz was 47 mpg on the motorway and that was 40 mph and in 5th gear.

I wanted to see how much I can get out of the car by driving like a nun.

Now I got myself a civic deisel 2.2 fuel economy better so is the acceleration



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Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: Jocko on January 11, 2018, 10:27:36 PM
The most I had on my mk 1 jazz was 47 mpg on the motorway and that was 40 mph and in 5th gear.
Wow! The worst I have ever had from my Mk 1 was 47.
Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: eagle123 on January 12, 2018, 10:16:20 AM
The most I had on my mk 1 jazz was 47 mpg on the motorway and that was 40 mph and in 5th gear.
Wow! The worst I have ever had from my Mk 1 was 47.
Sorry I meant to say I got 53 mpg on the gf jazz

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Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: eagle123 on January 12, 2018, 10:16:59 AM
The most I had on my mk 1 jazz was 47 mpg on the motorway and that was 40 mph and in 5th gear.
Wow! The worst I have ever had from my Mk 1 was 47.
Sorry I meant to say I got 53 mpg on the gf jazz

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Meant gd stupid autocorrect

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Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: peteo48 on January 12, 2018, 11:12:52 AM
That's amazing Jocko - your worst is better than my average (44.5)!
Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: peteo48 on January 17, 2018, 03:28:39 PM
Filled up yesterday. Just less than a mile back home. Have done a 1.7 mile trip today so 2.6 miles since fill up. Computer shows 36.5 mpg. Knock 10% off that and you have 32.85 mpg in real terms (ish).

Cold weather and short runs absolute killer so the 29 mpg in the OP is in the ball park for very short runs in cold weather and heavyish traffic.
Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: plasma on January 17, 2018, 04:10:54 PM
I always fill my tank to full. Until the first click off of the pump. The only way to get an accurate mpg figure is to fill the tank, zero the trip (or note the mileage - I do both), refill tank when fuel light comes on. Divide the miles covered by the gallons added to fill tank, and there is your mpg figure.

+1 yes that's how I allways do it.

Plasma
Title: Re: 29 mpg in 100% urban environment. Is this normal or what should I check?
Post by: peteo48 on January 17, 2018, 05:35:31 PM
+2

I've heard it said that different pumps might click off earlier or later but, over several fills, this will give you your actual mpg.