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Honda Jazz Forums => Honda Jazz Mk4 2020 - => Topic started by: stani on May 28, 2025, 12:36:53 PM

Title: Fuel Consumption
Post by: stani on May 28, 2025, 12:36:53 PM
What is your average fuel consumption?

I don't really like mine: 5,3 l (44,38 mpg). I've driven about 600 km (373 mil), 70% in the city.
It is also interesting that consumption dropped from about 5,9 l (39,87 mpg) to the current 5,3 l (44,38 mpg), mainly when driving outside the city, although it should be the other way around.
In the city I drive on "B"+"ECON". Outside the city on "D"+"ECON".  I ride with a "light foot".
Am I doing something wrong?

But the biggest shock was when I first took the car from the dealer. I drove about 200 km (124 mil), again with a “light foot”, only a small part on the highway. And at the end of the trip it showed me an incredible 8,2 l (28,68 mpg)!

Title: Re: Fuel Consumption
Post by: ninanina on May 28, 2025, 12:46:41 PM
I have the same thing stani

I mostly drive short distances in the city and it ruins the mpg as the engine hardly has time to warm up

As soon as I drive out of the city the mpg shoots up

The best mpg I’ve seen is about 74 which was part city, part A roads and part motorway and a much longer run too

I wouldn’t worry about it too much
Title: Re: Fuel Consumption
Post by: FMIB on May 28, 2025, 01:56:19 PM
Not checked the average for quite some time, but last time I did it was around 56mpg. The main use of my Jazz is very short 2-3 mile trips in and out of town, with the very(rare) occasional longer drive.
Consumption on cold starts during short journeys hurts the average, at times in the winter trips  can be mid 30's, whilst other trips I see 60's or low 70's with an all time high of 109mpg over 10 miles.

If the car is new, give it some time for the engine to loosen up a bit and I would switch off ECON mode as in my opinion it just forces you to press the accelerator harder. If you really are a light footed driver, you will do better with it off.
I use D most of the time to gain distance off throttle and pull it into B when slowing down for junctions, traffic lights, roundabouts etc to regain energy into the battery.
Title: Re: Fuel Consumption
Post by: Marmoset on May 28, 2025, 02:35:31 PM
What is your average fuel consumption?

I don't really like mine: 5,3 l (44,38 mpg). I've driven about 600 km (373 mil), 70% in the city.
It is also interesting that consumption dropped from about 5,9 l (39,87 mpg) to the current 5,3 l (44,38 mpg), mainly when driving outside the city, although it should be the other way around.
In the city I drive on "B"+"ECON". Outside the city on "D"+"ECON".  I ride with a "light foot".
Am I doing something wrong?

But the biggest shock was when I first took the car from the dealer. I drove about 200 km (124 mil), again with a “light foot”, only a small part on the highway. And at the end of the trip it showed me an incredible 8,2 l (28,68 mpg)!
I've done over 30,000 miles and for the last 25,000 or so miles, I've averaged 72mpg.

When I first got the car, the mpg figure was much lower.  Two factors: the car took some distance to run more efficiently and I learned how to drive it more economically. 

I never use the ECON button.  If you drive it as you want to drive it, the ECON button simply makes you drive with a heavier foot.  The car itself only needs the very lightest of touches with the foot.  My daughter, used to bigger, more luxurious cars, found the car to be surprisingly quick off the mark.  She was accustomed to using more foot pressure in her Mercedes, Jaguar and Range Rover.

I drive mostly in B mode, aiming to get as much of the regenerative charge into the battery, so that the ICE engine doesn't have to do all the work. 

The biggest part of driving economically for me is keeping my cruise speed quite low.  Trucks cover great distances at lower speeds.  I avoid driving as though I'm in a rush and will usually relax into driving at the same speed as trucks.  Obviously, this style of driving won't suit everybody, but I find it more relaxing and less tiring. 

Title: Re: Fuel Consumption
Post by: Downsizer on May 28, 2025, 04:13:05 PM
Stani - your picture shows a full tank (say 40 litres) and a range of 978 km. This suggests that the car thinks your consumption will be 4.1 l/ 100km (69 mpg). This does not square with the 8.2 shown for the last 240 km. Have you had some extreme weather conditions? What consumption can you calculate from your fuel purchases?
Title: Re: Fuel Consumption
Post by: stani on May 28, 2025, 04:21:08 PM
Stani - your picture shows a full tank (say 40 litres) and a range of 978 km. This suggests that the car thinks your consumption will be 4.1 l/ 100km (63 mpg). This does not square with the 8.2 shown for the last 240 km. Have you had some extreme weather conditions? What consumption can you calculate from your fuel purchases?
Then I filled up the tank at the end of the trip.
Driving conditions were normal.
The next time I fill up, I'll write down the data and check the actual fuel consumption.
But it is quite possible that it could be software (https://clubjazz.org/forum/index.php?topic=17635.0).
Title: Re: Fuel Consumption
Post by: Downsizer on May 28, 2025, 04:27:06 PM
I’ve just corrected my dodgy arithmetic- 4.1 l/100 km = 69 mpg.
Title: Re: Fuel Consumption
Post by: stani on May 28, 2025, 04:34:10 PM
I've done over 30,000 miles and for the last 25,000 or so miles, I've averaged 72mpg.

I drive mostly in B mode, aiming to get as much of the regenerative charge into the battery, so that the ICE engine doesn't have to do all the work. 
"B" both outside the city and on the highway?
Title: Re: Fuel Consumption
Post by: ahavoja on May 28, 2025, 04:42:14 PM
When my Crosstar was new, it also estimated around 1000 km range with a full tank. But since then the estimate has become lower, and nowadays it shows 700-800 km estimated full tank range. For the last 500 km my consumption has been 4.6 l/100 km according to the car, mostly at a speed of 50 km/h around city.
Title: Re: Fuel Consumption
Post by: ahavoja on May 28, 2025, 05:08:31 PM
I have a theory: Maybe when your car was new, it had been idling a lot at the dealership, burning petrol without moving anywhere. That could explain your high initial consumption 8.2 l/100km. The car has calculated this 8.2 l/100km averaged over the first 240 km that the car has ever driven. Now that you have driven more (600 km), the average has dropped to 5.3 l/100km.

I suggest to reset the trip meter, so the car would start calculating the average consumption from scratch, removing the possible effects of whatever happened at the dealership.
Title: Re: Fuel Consumption
Post by: stani on May 28, 2025, 05:19:26 PM
ahavoja: that's a good observation, maybe that was really the case. Because this Jazz was the only one at the dealer.
Title: Re: Fuel Consumption
Post by: coldstart on May 28, 2025, 05:21:42 PM
I never use the ECON button.  If you drive it as you want to drive it, the ECON button simply makes you drive with a heavier foot.

The accelerator pedal is not directly connected to the engine. It is merely an input device to let the motor control unit know your wishes. Pressing the ECON button changes the characteristic of the accelerator which means you have to depress it further to achieve the same level of acceleration.
This doesn't mean that you are using more power! - It just makes driving with a light foot easier.

ECON mode further somewhat moderates the climate control which in hot weather lowers the power consumption as well.

@stani:  I have found that cabin heat is a major spoil sport for fuel economy especially on short trips because it forces the ICE to keep running longer than necessary just to provide heat. It is more economical to use the seat heating and the heated steering wheel instead (if you have it).

Another "killer" for good MPG is speed. I've just returned from a 500 mile motorway trip to southern France and that has knocked off some miles from my average MPG. I keep one of my recordings on https://www.spritmonitor.de (just to show off) :D ;)


Title: Re: Fuel Consumption
Post by: stani on May 28, 2025, 05:45:48 PM
coldstart: so what do you advise? Use ECON or not? Use "B" (in the city/everywhere) or not?
Title: Re: Fuel Consumption
Post by: coldstart on May 28, 2025, 06:04:04 PM
coldstart: so what do you advise? Use ECON or not? Use "B" (in the city/everywhere) or not?

Well, it all probably boils down to personal taste...

I have now done 19'000 miles in ECON mode within close to two years of ownership (with probably less than a handfull of exceptions in NORMAL when I felt the rare need for a very speedy takeoff).

My "sturm and drang" period is well over and I prefer a relaxed and anticipatory driving style which incidentally is quite beneficial to fuel economy.

So, my choice is very clear: ECON mode "for the win" ;) and B-mode selectively when stronger decelaration is needed (like in dense stop and go traffic, going downhill or whenever in need to slow down more than D-mode offers).

You will have to experiment for yourself, what best suits your preferred driving style.
This is part of the "myth" that a new car has to "adapt" - imho, it is the driver who needs to adapt his/her habits to the car :D

Title: Re: Fuel Consumption
Post by: Downsizer on May 28, 2025, 06:09:16 PM
I use B except when I want cruise control, which requires D. I have used Econ since new, and haven’t tried driving without it.
Title: Re: Fuel Consumption
Post by: Jazzik on May 28, 2025, 06:09:40 PM
What is your average fuel consumption?

I don't really like mine: 5,3 l (44,38 mpg).

Stani, to start with, you are converting l/100 km to US gallons per mile. That's not done when you use a UK website! :D Better use Imp. gallon (UK). https://www.thecalculatorsite.com/conversions/fuelconsumption.php

Econ is only useful when you like to grow greenery on your dash screen:

(https://uploads.tapatalk-cdn.com/20211216/0e069103a3b79537590d4a703c9aaf2a.jpg)


I only drive in "D" when I want to use cruise control, otherwise always in "B". Just try and choose what suits you best.

As for consumption: give it some time, enjoy your new car and you will see that your Jazz is really economical. I keep track of my consumption on Spritmonitor: https://www.spritmonitor.de/ , visible here at the left.
Title: Re: Fuel Consumption
Post by: tfw7 on May 28, 2025, 06:53:12 PM
I have a 72 SR, had it from new so just over 2.5 years or so.
Mostly used for commuting to work (now 3x a week, was 5) - 10 miles each way. Plus 2 or 3 short 1-2 mile trips around town per week.
Longest drive it's ever done is ...err....about 35 miles.

Tank to tank average mpg never lower than 66, higher in summer to 72/73.

Experimented with ECON when first had car for a few months, but couldn't see any improvement, so never use it now. Reckon I'm quite light footed.
Rarely use heat.
Drive with a mix of B and D. Rarely get to high speeds - average speed on journey to work is usually under 30mph, with a 30sec burst on the dual carriageway to around 60-70mph!
Title: Re: Fuel Consumption
Post by: Nicksey on May 29, 2025, 07:31:04 AM
My 72 EX is now getting up to the 70 mpg mark again, now that the heater is no longer needed.
Even having the A/C on every now and then doesn't seem to affect the mpg in the same way the heater did.
Title: Re: Fuel Consumption
Post by: Lincolnshire Rambler on May 29, 2025, 08:12:10 PM
62.0 mpg over 56,300 miles 71plate SR
Title: Re: Fuel Consumption
Post by: stani on May 29, 2025, 08:29:55 PM
Lincolnshire Rambler: what are the values ​​"0.6" and "9.9"?
Title: Re: Fuel Consumption
Post by: Lincolnshire Rambler on May 29, 2025, 09:10:13 PM
That was when the car was new , think it was during the 1hour handover in dealer as the car controls explaned  . In tbat hour the petrol engine started up a coupke of times giving 9 mpg over 0.6 miles before i reset the A mode to 0 miles just round the corner from the garage . The A mode has never been reset since so the 56332. +0.6 miles is the distance travelled since new!
Title: Re: Fuel Consumption
Post by: Jazzik on May 29, 2025, 10:19:05 PM
I keep track of my consumption on Spritmonitor and it turns out that our Jazz is a bit optimistic about fuel consumption. The real consumption appears to be on average about 4 to 4˝% higher than our cars want us to believe.
Taking that deviation into account, 62 mpg on screen means an actual measured average consumption of about 59.5 mpg.
Not bad! (https://www.cheesebuerger.de/images/midi/froehlich/a052.gif)
Title: Re: Fuel Consumption
Post by: Lincolnshire Rambler on May 30, 2025, 08:12:56 AM
Yes even 59 mpg is good over 56,000+ miles as its across 3 winters and every road type encountered . I often plant foot to floor to enjoy the jazz zooming away from traffic lights or roundabouts so i dont drive with economy in mind all time by any means !😁😁😁
Title: Re: Fuel Consumption
Post by: aphybrid on May 31, 2025, 08:43:32 AM
Surely this topic covered comprehensively elsewhere - under MPG For Those Interested.
Title: Re: Fuel Consumption
Post by: Marmoset on May 31, 2025, 09:45:04 AM
I've done over 30,000 miles and for the last 25,000 or so miles, I've averaged 72mpg.

I drive mostly in B mode, aiming to get as much of the regenerative charge into the battery, so that the ICE engine doesn't have to do all the work. 
"B" both outside the city and on the highway?
Yes, nearly all the time.  It hasn't broken the car yet!
Title: Re: Fuel Consumption
Post by: Kremmen on May 31, 2025, 10:35:15 AM
I've never used D, far prefer the one pedal driving in B

and that's after driving auto's since about 1972 when it was D mode all the time so I'm used to both
Title: Re: Fuel Consumption
Post by: ninanina on May 31, 2025, 04:47:28 PM
Strange because I never use B mode

If I’m going down a very steep hill then that would be the one and only time I’d click into B to give more engine braking.  It happens very rarely

I was the same when I owned my last two Prius and only used B for steep descents
Title: Re: Fuel Consumption
Post by: stani on May 31, 2025, 06:17:41 PM
The Honda dealer told me: city "B" outside city "D". You can't put cruise control on "B".
Title: Re: Fuel Consumption
Post by: Kremmen on May 31, 2025, 06:23:54 PM
You can't put cruise control on "B".

Another reason to use B, I tried ACC a few times early on and had issues with it thinking vehicles in adjacent lanes were in front so slowing me down
Title: Re: Fuel Consumption
Post by: ninanina on May 31, 2025, 06:45:45 PM
Never had any issues when using the smart cruise control;  ACC

The car seemed to lock onto the car in front and modulate the speed accordingly; it had no drastic braking or acceleration just a smooth transition

The few times I’ve used ACC it was perfect and so relaxing
Title: Re: Fuel Consumption
Post by: Jazzik on May 31, 2025, 08:40:41 PM
I tried ACC a few times early on and had issues with it thinking vehicles in adjacent lanes were in front so slowing me down

Off topic of course, but I've never experienced anything like this, it looks like your camera isn't 100% aligned...

(https://www.toyotahybrideforum.nl/images/smilies/icon-ontopic.gif)
Title: Re: Fuel Consumption
Post by: Kremmen on June 01, 2025, 05:49:26 AM
Maybe

As I've posted before, years ago, on a motorway which is where I've only ever used it, I pulled out into an overtaking lane and even though I was a fair way behind it slowed me down to the speed of the vehicle I was overtaking.

Then when I pulled further across with offside wheels almost on the line between lanes 2 and 3 it suddenly released the block and accelerated hard to get me back to the set CC speed

I've seen a couple of other posts with similar problems

I find LIM the best option as it works just like CC used to but you need to keep the loud pedal pressed which isn't a problem

Title: Re: Fuel Consumption
Post by: Nicksey on June 01, 2025, 07:27:08 AM
I use ACC on a regular once weekly M route, and find it easy and clever. If I come up to a slip road that enters my lane, I hit 'cancel'... and once past any merging vehicles I press the + and off I go. Similarly, if I am not happy letting the camera keep me at whatever vehicle's speed I am following, 'cancel' then floor it, and back to +.
Sometimes, I just use the accelerator to negate the ACC... all good.
Title: Re: Fuel Consumption
Post by: Lord Voltermore on June 01, 2025, 09:13:44 AM
ACC could be  bit 'manic' on earlier mk4's  which, once the road ahead is clear,  tend to use near  full throttle to regain any lost speed as quickly as possible. Noisy and not fuel efficient.     I tended to overide this by using  manual throttle to regain lost speed more gradually  before allowing ACC to resume  the 'donkey work' .

This has been improved and toned down  on 'Facelift' cars from 2023 which now regains speed briskly enough but without revving the nuts off the engine. :o

I use ACC quite a lot and find it very useful, not just saving you having  a foot on the 'loud' pedal.  It reacts to the presence of other vehicles , and can sometimes  be hesitant about t a vehicle in an adjacent lane ,and might take a few seconds  before it 'decides' the road ahead is indeed clear of vehicles before regaining speed .Even though the driver may know its ok. It errs on the side of caution.

 Conversely an experienced driver may sense from the behaviour of other drivers, or circumstances, that they may be about to  change lane suddenly, or you may spot traffic stopping ahead before the ACC radar would detect anything happening.  . So you need to work with the system, know its limitations, and treat it as a drivers aid ,not a self driving car.   But ultimately ,worldwide a few crashes and  and deaths may be prevented  when a driver loses concentration, or is slow to react . You may drive for a lifetime and not need it,but the same could be said of a seatbelt.
Title: Re: Fuel Consumption
Post by: stani on June 06, 2025, 01:49:32 PM
I have a theory: Maybe when your car was new, it had been idling a lot at the dealership, burning petrol without moving anywhere. That could explain your high initial consumption 8.2 l/100km. The car has calculated this 8.2 l/100km averaged over the first 240 km that the car has ever driven. Now that you have driven more (600 km), the average has dropped to 5.3 l/100km.

I suggest to reset the trip meter, so the car would start calculating the average consumption from scratch, removing the possible effects of whatever happened at the dealership.

So I tried it and it apparently helped.A few days ago I reset both odometers and also reset the driving cycle value (Econ).
And the result is here, see the attached pictures.

If I calculate the consumption based on refueling and kilometers traveled, then my consumption comes out to be about 3.9l/100km.
The next time I refuel, I'll register at SpritMonitor and see it more accurately.
Title: Re: Fuel Consumption
Post by: Kremmen on June 06, 2025, 02:33:40 PM
Forget Eco, it dulls the throttle so you need to press harder

I've always achieved better MPG with it off and using a light right foot
Title: Re: Fuel Consumption
Post by: coldstart on June 07, 2025, 05:59:05 PM
Forget Eco, it dulls the throttle so you need to press harder

ECO only the changes the characteristics of the throttle (there is no direct connection to the engine!)

imho it all boils down to personal taste - and I kind of like the "dulled" throttle response.
Even in ECO-mode the Jazz is by far the most "responsive" car I've ever owned and I'm not feeling to "miss out".

I found its drive train to perfectly support my preferred anticipatory and relaxed driving style (which is an additional bonus at the
petrol station - and:  my tyre vendor hates me for it) :D

(btw I'm about 6 mpg ahead of you) :D ;)

Title: Re: Fuel Consumption
Post by: Hicardo on June 07, 2025, 09:21:10 PM
I'm a NORMAL guy, but that is a matter of opinion. ECO to me just makes the car feel duller, and offers no mpg advantage, i've tested it.  :o. I'm also a D kinda guy.  Use B on steep downhills, thats it.   :)
Title: Re: Fuel Consumption
Post by: coldstart on June 07, 2025, 09:25:16 PM
I'm a NORMAL guy, but that is a matter of opinion. ECO to me just makes the car feel duller, and offers no mpg advantage,

imho it all boils down to personal taste - and I kind of like the "dulled" throttle response.

As I said: It is a matter of taste!   -   no offense!   -   (I still prefer the "dulled" mode)  :D

(and I seem to have the "advantage" of quite a few mpg over you as well) ;) - just a small hint for you: cabin heat is an absolute killer for mpg in the cold!



Title: Re: Fuel Consumption
Post by: ahavoja on June 07, 2025, 10:43:53 PM
cabin heat is an absolute killer for mpg in the cold!
Indeed it is. Especially on short city trips when Jazz can't stay in EV mode, because the cabin requires heat from the petrol engine. But on long motorway cruises the cabin heat shouldn't affect MPG much, because the petrol engine is running most of the time anyway producing plenty of waste heat.
Title: Re: Fuel Consumption
Post by: Kremmen on June 08, 2025, 05:12:52 AM
My MPG is what it is because since moving my normal max journey is only 5 miles

I did go out last week to top up the HV battery as the car had stood for 3 weeks and on that 50 mile journey it returned just over 70mpg
Title: Re: Fuel Consumption
Post by: stani on June 08, 2025, 05:50:49 AM

I did go out last week to top up the HV battery as the car had stood for 3 weeks...

Oh, can the HV battery be recharged? How and where?
Title: Re: Fuel Consumption
Post by: Kremmen on June 08, 2025, 07:28:53 AM
The only way we can charge it is to go out for a run of at least 30 miles/minutes at least once every 3 months according to the manual :

Title: Re: Fuel Consumption
Post by: ahavoja on June 08, 2025, 09:08:30 AM
There is also another way to recharge the HV battery, by putting gear selector to park (P), and then holding the accelerator pedal floored down for longer than 10 seconds. The engine starts and begins charging the HV battery as long as you keep the pedal floored.
Title: Re: Fuel Consumption
Post by: John Ratsey on June 09, 2025, 08:26:58 AM
ECO only the changes the characteristics of the throttle (there is no direct connection to the engine!)
ECO also widens the acceptable difference between target and actual cabin temperature before the system turns on the engine to provide cabin heating.
Title: Re: Fuel Consumption
Post by: Kremmen on June 09, 2025, 09:26:53 AM
Yep, on a hot sunny day with the sun heating the moving car the AC in Eco mode just lets the cabin get hotter and hotter

It can work a bit harder if you set the ideal temp to Min but setting say 20C and it never gets there

Been the same on all Hondas I've owned since 2007