What is "Carson cruise" and can I determine it myself?
From this highly reliable web page http://www.eaa1000.av.org


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The maximum range airspeed may be the most economical way to fly, but it's quite slow... Hence, we may consider the speed for which the ratio fuel flow/knot of airspeed reaches a minimum. That speed, marked by the point where a line from the origin is tangent to the thrust required curve, is called 'Carson's speed'.


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In s/l flight, drag = thrust. Hence, the lower graph shows the 'thrust required' curve. There is a fixed ratio (1,316) between the maximum endurance speed, maximum range speed and Carson's speed, so that:

Maximum range speed = 1,316 x Maximum endurance speed

Carson's speed = 1,316 x Maximum range speed

That's a simple way to find Carson's speed for your plane. You can get the value of the Max. range speed from the POH