How accurate is the MPG indicator.??

[Jocko]

On board display (reason for this thread) measures fuel used and miles traveled and doesn't give a whit if it is cold and wet or dry and sunny, nor whether there is one in the car or five large adults.

[John Ratsey]

I do find the WLTP figures a lot more real world than the old NEDC figures. I think the combined figure for my car is 46.3 on WLTP and I get around 42 mpg but, to be fair, my usage isn't really balanced with the majority of my journeys being 3 to 5 miles.

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.

High means up to 60 mph. Extra-high is representative of driving at around / over the UK speed limit See https://en.wikipedia.org/wiki/File:Class_3b.svg

I find that in warm dry weather my Crosstar delivers (based on fuel into tank) close to what the WLTP data say it should based on proportion of time / distance in the different sub-parts. WLTP, however, lacks a cold weather cycle and this is needed, if only to encourage manufacturers to incorporate measures to improve cold weather fuel economy. such measures exist and don't cost much but there's no commercial incentive to include them. Wet roads also seem to upset my Crosstar's fuel economy. All tyres have to push water out of the way but perhaps some are worse than others.

EVs do have a problem with over promising and under delivering on a truly epic scale. Here WLTP seems some way from reality. The Honda E is a sub 100 miles car and yet, I think, the WLTP figure is about 135 - it's hard to imagine how perfect the conditions would have to be for a Honda E to attain that.

WLTP for EVs suffers even more than with ICEs when power is needed for functions other than moving the vehicle. Heating / aircon is the biggest drain but lights / wipers etc all need power. EVs used on slow journeys will be using bigger proportion of the battery power for these other functions. An hour's worth of heating (for example) needs the same amount of electricity whether driving 10 miles or 50 miles.

[culzean]

Based on this and a bit of online research it now seems that EV's are totally unsuitable for longer journeys. If you can only fast charge once on a journey then the useable range is dramatically reduced.
Has this been hidden by EV makers or is this information only just being understood by the industry?

Lots of weasel wording used in adverts, like 'up to XXX miles range',   and 'can charge to 80% in 30 minutes' ( what is the level when charging is started, 20% or 70% ? - also Li-Ion battery can charge to 80% quite quickly,  but it is the remaining 20% that can take quite a while ).  Even Tesla ( the biggest advertiser of fast charging ) admit that fast charging not good for batteries and can shorten battery life quite a bit if used too often.   There are limitations to batteries that have been known about for a long time, but never passed on to the people thinking of getting an EV, and the car makers are certainly not going to advertise the limitations and drawbacks.  Keeping a Li-Ion battery plugged in and fully charged can also shorten battery life ( Li-Ion actually like to be kept about 50% charged for longest life ).

[nowster]

( Li-Ion actually like to be kept about 50% charged for longest life ).

It's usually between 50% and 80%.

[culzean]

( Li-Ion actually like to be kept about 50% charged for longest life ).

It's usually between 50% and 80%.

even lower than I thought 40% is best.....

https://zeusbatteryproducts.wordpress.com/2012/08/22/5-best-storage-and-charging-tips-for-extending-lifespan-of-lithium-ion-batteries-in-home-business/