lies, damm lies and statistics.
you need to understand how the calculation is made as this will show you why the range is very misleading and you were never going to achieve the figures you quoted.
basically, the range will look at how much fuel you have left, then
using the most RECENT data, (ie based on only the last few miles of driving) it will give you a range.
That means, to get the range its stating you need to achieve the same MPG as you did in the last few miles for every miles you cover for the rest of the tank.
So in this case, it likely calculated the range using data when driving on A roads with a fully warmed up car and probably averaging around 55mph and may including slowing down at the end of the journey; so its cherry picking the best period of mpg and ignoring that for the remainder of the drive the mpg achieved was far worse.
The minute you stop its all over. - as soon as you start the next drive the car isnt warm, the range will plumet, which i think you saw.
If you want to test this if you are driving fairly briskly you could get the range down to zero, but if you then drive very carefully the range can increase as it will then be calculated on the more recent more economical figures.
an example:
lets say your typical drive is 15 miles.
the first 5 miles you may only get 20mpg as the car isn't up to temperature
the next 5 miles 30
and the last 5 40mpg.
when you finish the drive the range will be based on 40mpg. but you have not achieved 40mpg over the journey, the actual mpg achieved over-all is much
lower.
(if you think this example averages 30mpg average you are wrong. its more like 27.7mpg and which is why many people believe they get better mpg than they actually do.
and in case you doubt this:
miles covered / MPG achieved / gallons used
10.......................20......................0.5
10.......................30......................0.333333333
10.......................40......................0.25
total gallons used.........................1.083333333
total miles covered.......................30
30 / 1.083333333.........................
27.69 (2dp)
As a rough
guide per tank (based on LCR filled up and running to 10 miles or so past yellow warning light).
360 miles to a tank just about gets 30mpg
420miles to break 35mpg
a whopping 480 to break 40mpg.
I remember going to Blackpool from bham and back on £20 in 2004 I think,so dose that mean my little metro was good on mpg or was it because of cheap petrol and there was no trip computer on that!!
