Today during the ground portion with my instructor he asked me "why did you choose to cruise at 2300 rpm flying at 1990 ft pressure altitude?" I didn't have an answer for him, and I couldn't find anything in the POH or online that could answer that question.
All I was able to find and surmise is "cruising should be done between 55% and 75% power, it is up to the pilot's discretion to choose the power setting in this range for the planned route"
So now I'm stuck with this in my head:" As long as my power setting allows me enough range and endurance to reach my destination with reserves in mind and that my cruising speed is not ridiculously slow any power setting between 55% and 75% should do"
However, previously another instructor told me for a C172 a power setting between 62% and 65% is the best balance between performance and engine care.
what is the right way of going about this?