On the road fuel quality
 

I don't know if there's another thread about this or if this the right place but we've had some issues with fuel along our way. Firstly while we were in Hungary we noticed a massive drop in our range. We're both riding very different bike, a BMW single and a KTM Adventure (EFI, both). We both noticed a 30% drop at least. Mine didn't seem to lose any power but the KTM ran very lumpy at lower revs. A little redex and a full tank of gas in Serbia seemed to sort the issue out on both machines.
In Iran the fuel is very different. We're seeing far better range, even better than normal. I'm noticing a 10% increase in range with no difference in power and the KTM is running fine. The only issue is on both bikes when revved hard, they pink, quite noticably. Neither did it before. We're heading through Pakistan and India, does anyone have any idea what the fuel is like there, any issues we should watch for?

I noticed an improvement in fuel consumption in Iran, in fact at one point my R80GS was doing 80-90 mpg if the figures were to be believed, at this point I realised the meters on the pumps were totally inaccurate and they were giving more than they recorded. It might be possible that your drop in mpg was caused by pumps giving short measures given the level of the decrease, although I have had a similar thing in Egypt when I accidently put 80 octane in my bike and it ran badly.

Varying consumption could also be to do with altitude.

However, to the main point of the thread, fuel quality certainly varies in Russia, particularly away from major cities. Once I and a co-rider both filled up and we complained to each other about foul smelling exhausts (bikes!) until our next fuel stop, from when it got better.

The other interesting thing I have noted here - my F650GS/D has a listed fuel tank capacity of 17.3 Litres.
Once I managed to fill it and therefore pay for over 19 litres.

Concentrated fuel? Or just plain profiteering?
Not that it matters too much here with fuel at 60pence(UK) a litre, however much you get!