Just drive smoothly and naturally.
Sometimes I think my FC too high and drove like auntie but get worse result. Other time just drive fast fast fast and get good numbers.

I think the major impact is big difference in acceleration and decelaration. Fast acceleration and then follow by deceleration means waste fuel. If you think about it, if you drive at 80KMH flat, you use less fuel but ur distance doesnt change. So you drove longer which then means more fuel as well. Its almost impossible to derive a formula to actually calculate these precisely.