Over the last 6 years, pretty much to the day, I have averaged 16.67 Ks per litre, or 48 MPG, or exactly 6 L per 100 Ks. speeds were around 100 - 120Ks usualy. Average speed is about 85 Ks, though I dont have data for that.
Any one who has studied statistics, will know that the data having been taken over 6 yrs at every fill up (usualy every week) over 118801.50 Ks means that continued sampling, isnt going to change the the average result isnt going to change by any appreciable amount.
so to plan for 1250 Ks , I would expect to use 75 Litres. formula is D(istance to go) x L(iteres per 100) / 100.
(1250*6)/100 = 75 Liters required. Average expected range to reserve (orange light) was about 400 Ks, and to empty about 500 Ks.
So, if we ride to orange light, we can expect to take about 20 liter of fuel, and a 15 liter top up on arrival.