Thanks for the reply. I did the same by looking at the POH but nothing specific there. In the end I assumed a linear relationship between the 7 and 10 gallon consumption and KIAS for max range ie at max range KIAS consumption would be 7 gallons as that's the most efficient use of fuel hence max range. But for any calcs, just to be safe I use 10 gallons now though. I was just trying ti make sure I hadn't missed something obvious.