Now after tuning I calculated my GD's fuel average which is very good I think..
In Reserve at 1254 kilometer..
Odometer 0 then I fill up my tank with 4.77 litre fuel..
then it hits reserve at 1508 kilometers..
So here is the calculation..
1508-1254 = 254 kilometers
254 / 4.77 = 53.24
I think its more than good...isn't it??