i have 3004 cultus. i get average in city with AC 18 km per Kg.
how i calculated average. first of all i emptied my cylinder. then i refill and noted total fill by Kg. and then odometer to 0 when again CNG finished see how much killometer vehicle did in that CNG which was filled. now divide Killometer by kg that will be correct average of CNG per KG.
in full cylinder or in Rupees does not mean any thing in my opinion.