Any - Posting in Honest John Real MPG - Firmbutfair

This is more of an apology than a complaint. I have recently submitted my real mpg figures to the HJ database for my car, whilst logged into my HJ account only to note a considerable delay (e.g. more than 10 hours on 9 April 2017) between submission and the data being updated for my model. On at least 2 occasions this year, I have logged out and then re-logged in and re-submitted my data in the belief that maybe my log in had 'timed out' and the data discarded. On checking my profile much later, I can see both submissions listed so I must apologise for my impatience.

As a general question, it would be good to know whether duplicate entries to the real mpg database are flagged to an administrator at HJ such that only one is actually added to the figures from which the overall running average is calculated.

In any event whilst the integrity of the Real MPG data relies on our submissions being honest, it is clear that individual results achieved will depend very heavily on such things as driving style (heavy versus light footedness), geographical location (flat or hilly), passenger payload, and the levels of traffic congestion typically experienced by individual owners. Anyroadup, here's a big thank you to HJ and the team for hosting the best site for keen motorists and for helping to inform the car purchasing choices that we make.

Edited by Firmbutfair on 22/05/2017 at 22:21

Any - Posting in Honest John Real MPG - Avant

Thanks for your comments. I'll ask and see if anyone at HJ would like to answer this.

Any - Posting in Honest John Real MPG - Engineer Andy

I agree with your points about driving style and the type of driving done - I'd made a very similar set of observations on another thread some time ago. The Tyre Reviews website takes into account driving style, and I think HJ's should on the Real mpg page.

I also think we should have the ability, through our login, to update our own submissions, as (similar to the tyre reviews on the other website) cars change their mpg as they age, and often quite appreciably over the first year as the engine wears in (normally for the better).

Many people we see complaining about their car's mpg often do so soon after purchasing it, quite often when its new, so inputting such figures can give a false result, similarly as the new owner gets used to the car even if its not brand new.

Whilst I appreciate there are lots of variables and we may not be able to include them all to get a hyper-accurate result, perhaps the following should be at least discussed, though whether its too late after the real mpg database is now quite large, I'm not sure.

Variables for car use that affect mpg:

  • Driving style;
  • Length and type of journeys predominantly driven (including type of road driven on);
  • Load in car (weight of driver and passengers plus boot load) normally used;
  • Type of weather (incl. whether the heater or A/C is regularly used) and traffic conditions experienced when driving;
  • Age of car;
  • Grade of fuel used;
  • Tyres used, including type/model, age and wear;
  • Whether a roof rack/box or trailer is fitted/regularly used.

Many of the above might only make a small difference for most of us, but for some people, they could make, either individually or combined, huge difference - for example a retired person owning a car and occasionally doing a longer journey to friends outside the rush hour would like do a far higher mpg than a parent driving the same car with kids going to a local school and the shops a lot. I suppose at least HJ's page has a range of mpgs quoted as well as the average.

Any - Posting in Honest John Real MPG - RobJP

I would disagree. Complexity breeds confusion. Add in dozens of variables, loads of data entry points, and you'll just end up with mistakes being made (making your 'more precise' figures pointless), or alternatively you'll get people not bothering because there's too much data to enter.

KISS, as the engineering maxim goes. It's not supposed to be a "You WILL get this mpg", but a "this is a rough guide to what you will get"

Any - Posting in Honest John Real MPG - Engineer Andy

I would disagree. Complexity breeds confusion. Add in dozens of variables, loads of data entry points, and you'll just end up with mistakes being made (making your 'more precise' figures pointless), or alternatively you'll get people not bothering because there's too much data to enter.

KISS, as the engineering maxim goes. It's not supposed to be a "You WILL get this mpg", but a "this is a rough guide to what you will get"

I probably answered my own question with the range of mpgs comment at the end. I would still advocate not registering our cars' mpg until we've run it for at least 6-12 months, especially brand new cars, for the reasons I gave earlier. My car's mpg improved by 10% from the first to second year, despite it being used in the same way.

Any - Posting in Honest John Real MPG - Firmbutfair

Thanks for your responses. I agree with Engineer Andy - the range of real mpgs submitted gives an indication of how much economy can vary across the population of owners and driving conditions. e .g. for one particular 5 door hatchback of interest, the range reported was between 40 and 54 mpg with over 80 submissions made for the whole range of models with an average of 45.4 mpg but 3 weeks later this has changed to 37 to 54 mpg and the average has dropped to 44.4 mpg with submissions for the whole model range now at 85. All quite understandable. Using the built in Trip Computer in my current car, clearly indicates the significant drop from a 57 mpg average over a 93 mile round trip on B roads (to avoid weekend road closures on the main trunk roads) falling to 53 mpg once the oddomoter had reached 106 miles after completeing a short local trip in town in start stop traffic. My arithmetic indicates that the average for the short local trip was around 35.3 mpg.

Overall 'brim to brim' calculations indicate around 49 mpg of mixed driving and to date surprisingly good agreement between the Trip Computer average displayed and the 'brim to brim' calculation over typically between 400 and 500 mile intervals every 3 weeks or so. It is also quite likely that retired persons may get better than average fuel economy if they use their cars sparingly and choose to only travel outside peak congestion times.

I can see that bragging about the 50+ mpg fuel economy from our Matsus***a 1500 is the new game for all the law abiding, speeding aware citizens of the British Isles!

Edited by Firmbutfair on 23/05/2017 at 14:20

Any - Posting in Honest John Real MPG - SteveMegson

Don't worry, you won't do any harm by submitting duplicate values. We do identify duplicates and combine them before calculating the overall average.

There's a tricky balance between asking for lots of details about each person's driving or trusting that these factors will balance out in the average if we have enough submissions. The more questions we ask, the more likely it is that people don't bother to fill in the form or just enter a guess that sounds about right. There are, for example, a suspicious number of people driving 10,000 or 12,000 miles per year.

Having said that, there will certainly be models which are more likely to be driven in town and others which are more likely to spend all their time crusing on motorways, and parts of the country where people consistently get better or worse MPG. We can definitely see a seasonal trend in results. With all these factors, the challenge is really deciding how to present the data in a useful way.

Any - Posting in Honest John Real MPG - Firmbutfair

Many thanks for your reassurance Steve and the associated observations and feedback re the data and seasonal trends etc. Once again - HJ and the team doing an excellent job keeping the motorist fully informed. Thank You all.

 

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