Author Topic: MPG for those interested.  (Read 172774 times)

John Ratsey

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Re: MPG for those interested.
« Reply #375 on: September 11, 2020, 02:46:39 PM »
Just had another fill up that was very close to the computer and I'm now wondering if the CVT removes some of the variables in a manual.
I’ve not found that - see my 3 year figures in a quote from 2019:  “I’ve just completed 3 years and 30636 miles, using 2738 litres of mainly ASDA 95, giving 50.9 mpg.  Trip B has been running throughout without resetting and is showing 55.8 mpg, a discrepancy of 9%.  Average speed shown as 35 mph.”
My year and 5000 miles of a CVT Mk. 3 Jazz also showed 9% optimism by the computer. I have to wonder if it was programmed to show a nice increase in mpg compared to the Mk. 2 Jazz. In contrast, my HR-V was only 3% optimistic perhaps because there was no need to show an improvement over a previous model. I'm convinced that some bias is programmed into the calculation. If there wasn't then, on average, half of drivers would get a computer mpg that was below the reality.
2022 HR-V Elegance, previously 2020 Jazz Crosstar

Downsizer

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Re: MPG for those interested.
« Reply #376 on: September 11, 2020, 04:10:23 PM »
I think manufacturers are making sure they can't be blamed for speeding incidents.

John Ratsey

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Re: MPG for those interested.
« Reply #377 on: September 12, 2020, 04:36:27 PM »
I think manufacturers are making sure they can't be blamed for speeding incidents.
I've found the odometers on my recent cars to agree very closely so it's not miles being shorter than the real distance in order to show more of them. Also, I think if you compare the speedometer to GPS speed then you'll find that the difference between display and actual is fairly constant (1 -2 mph) throughout the speed range so this safety margin is added in just before the speed is displayed.
2022 HR-V Elegance, previously 2020 Jazz Crosstar

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Re: MPG for those interested.
« Reply #378 on: September 13, 2020, 11:16:47 AM »
Compared to GPS my display is about 4 mph high at 70 mph.  My impression is that it’s 4-5% high across the range.  I set the cruise control to 42 in a 40 limit.  The tyres are near the end of their life which may account for a bit of the gap.

Jocko

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Re: MPG for those interested.
« Reply #379 on: September 13, 2020, 11:42:23 AM »
I have 3 GPS speed displays in front of me. My GPS Speedometer, my Dashcam and my Garmin 51. The GPS Speedometer and the Dashcam always read the same but the Garmin always reads 1 mph lower. I go by the majority. Perhaps the Garmin has so much more processing to do. It is quite handy because when the Garmin chimes to say I am exceeding the limit I know I am just on it.

peteo48

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Re: MPG for those interested.
« Reply #380 on: September 14, 2020, 05:44:20 PM »
Just had my best tank after our weekend break. 271 miles giving an average of 55.1 mpg actual. This showed as 58.9 on the fibometer. Average speed over the tank was 38 mph.

I notice that my mpg over the last 10 fill ups is 46.5. This is almost exactly the same as the WLTP combined figure of 46.3 for this particular model. I guess that indicates that WLTP is a substantial improvement over NEDC.

John Ratsey

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Re: MPG for those interested.
« Reply #381 on: September 14, 2020, 09:44:44 PM »
It's informative to look at the test results for the different parts of the overall WLTP score. Numbers for the Mk 3 Jazz are at https://www.honda.co.uk/content/dam/local/uk/cars/WLTP-PDF/19YM%20JAZZ%20-%20WLTP%20Data.pdf . Wikipedia https://en.wikipedia.org/wiki/Worldwide_Harmonised_Light_Vehicles_Test_Procedure explains the different components:

The WLTP is divided into 4 different sub-parts, each one with a different maximum speed:

    Low, up to 56.5 km/h
    Medium, up to 76.6 km/h
    High, up to 97.4 km/h
    Extra-high, up to 131.3 km/h.

These driving phases simulate urban, suburban, rural and highway scenarios respectively, with an equal division between urban and non-urban paths (52% and 48%).


If most of your driving is in the most efficient WLTP zone then it's possible to get better than the WLTP numbers.

However, the WLTP testing temperature is 23C which doesn't provide manufacturers with any incentive to improve cold weather fuel economy https://www.honda.co.uk/cars/owners/wltp-testing.html .

2022 HR-V Elegance, previously 2020 Jazz Crosstar

peteo48

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Re: MPG for those interested.
« Reply #382 on: September 15, 2020, 12:44:19 PM »
Yes - I think that is spot on John. I would expect to get over 50 mpg on average if I didn't do so much stop/start stuff.

Might struggle to attain Jocko levels though :P

Redstart

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Re: MPG for those interested.
« Reply #383 on: September 27, 2020, 10:00:36 AM »
I've had my 68 Jazz manual S for 3 months.  Averages 55 on the odo. Just done a 65mpg on 125mile motorway trip.
Not gotten round to brim to brim yet. Cracking car that could do with a little more room for the driver. (I'm 6'4" though!!)

Downsizer

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Re: MPG for those interested.
« Reply #384 on: September 27, 2020, 12:10:46 PM »
I've just completed an 8-day tour of the Lake District, travelling to and from Suffolk (via Barnard Castle of course).  The overall fuel consumption was a pleasant surprise, though a brisk northerly wind on the return journey may have helped!  The true consumption was probably about 58 mpg.

peteo48

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Re: MPG for those interested.
« Reply #385 on: January 27, 2021, 10:41:09 AM »
Just had my lowest ever mpg in all the Jazzes that I've owned. 31.3 mpg actual (35.6 on the fibometer). In fact it's my lowest mpg in any car for more than 10 years.

I'm not overly concerned. The combination of lockdown and a colder than usual winter and an average speed of 13 mph tells you that the car has rarely done more than a shopping trip and I have had several sessions with the car stationary ticking over whilst I cleared windows in and out. It also had it's first service and garages do tend to have the car running whilst stationary.

Jocko

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Re: MPG for those interested.
« Reply #386 on: January 27, 2021, 10:47:09 AM »
Ouch. That is a low one. The lockdown and cold weather is a pig.

TnTkr

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Re: MPG for those interested.
« Reply #387 on: March 01, 2021, 08:05:43 AM »
We did about 320 km (200 miles) road trip yesterday. Highway and country road, wet, slush, snow and ice. Very beautiful sunny weather, +6 °C. Average speed 75 km/h (46.7 mph). Fuel consumption 5.1 l/100 km (55 mpg) according to dasboard, 5.2 l/100 km (54 mpg) calculated from fill-up.
« Last Edit: March 01, 2021, 08:12:22 AM by TnTkr »

Downsizer

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Re: MPG for those interested.
« Reply #388 on: March 26, 2021, 05:30:24 PM »
I've just bought fuel for the first time since 17 December.  Only 280 miles covered and 34 litres needed, giving 37.5 mpg, by far the lowest figure I have ever recorded, but not surprising given that the average journey length was probably about 3 miles and in winter. The fibometer recorded 43.5 mpg.

peteo48

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Re: MPG for those interested.
« Reply #389 on: April 27, 2021, 12:14:16 PM »
I was always very anti the CVT transmission until I actually got one. I think one reason for my poor mpg at times (even allowing for the short journey in the winter thing) is coming to terms with the best way to drive them. To overcome an initial sluggishness, especially at the lights, I've been in the habit of opening the throttle in a rather heavy footed way. I've been looking into various techniques to maximise fuel economy with the CVT and the key seems to be "linear" throttle inputs - squeezing the pedal rather than a more aggressive stamping on the pedal approach.

It's blindingly obvious really and it was how I used to drive manuals with the imaginary egg between foot and accelerator. I'm finding that the "linear" approach is absolutely the way to drive a CVT and this avoids the rubber band effect where the engine roars up the rev range with little result in terms of acceleration. The car actually seems to move off the line more briskly and higher gear ratios are achieved earlier as well.

More squeeze less stamping!

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