Peugeot 208 world record

[RetroPug]

But as I've proved, weather, season etc doesn't really make a difference to an overall tank average.  Yes if you drive in torrential rain/floods/wind for 10 miles and check the mpg it'll be less than if you did the same 10 miles on a clear day, but over a 600 mile tank of mixed weather and roads and traffic it evens out.  The small differences really aren't noticeable on that large scale.  Fuel also doesn't make a difference.  Or tyre pressures which I must admit surprised me.  Or even chucking a toolbox and various stuff in the boot.  I've always checked MPG but never recorded it before like I have with the Focus, and been amazed how it's so nearly the same regardless of any external factors!  There will be exceptions as a I said, someone that does solely town driving for example, but their result is still useful...for others that do solely town driving.

I get the same MPG on the Focus in the 'flat counties' as a guy in Scotland...and as most other people on that forum.

I see your point that there are too many variables for it to be a really accurate test...but who cares?  It's more pointless doing a test where no-one can replicate it.

That's indicated MPG which isn't necessarily accurate.
 
None of those seem to make a difference when you drive a whole tank, but if the MPG did vary and there were several variables you wouldn't know which had caused it.

I'm not trying to say real-world MPG is a bad or useless measure, I'm saying it isn't very useful for a manufacturer when developing a vehicle, and for marketing purposes I think they'd also rather have a very high number.